The Role of Flow in Web Design

By Scott Berkun, May 2001
When things are going well in life, you move through processes without thinking about them. At the point at which you master a skill and can do it without thinking, you are able to use your mind for more advanced kinds of activities. Learning to type, or to drive a car, takes time, but once you obtain the skill you are free to pursue the high-level goals of writing an essay or driving to the beach. In designing Web pages, or anything that people interact with, a prime goal must be the achievement of flow for the user: Enable them to transcend the mechanics of links and navigation, and focus completely on what they want to achieve.

To achieve flow, you have to invest from the first day of your project. Every page and every element of your site has to be created with the user's perspective at the core of your thinking. The easiest way to achieve this is through asking questions of your sketches and designs as you create them, before you bring them into the usability lab. Use these questions as seeds of discussion for brainstorming, and for comparing and generating alternative ideas. There are two kinds of questions about flow: What is the site structure and what is the task your user is trying to achieve?

Flow in Site Structure
When considering designs for an entire Web site, or just key elements like the home page and navigation systems, you must have knowledge about the common activities your users need to do. You can probe for your high-level flow by considering the follow questions in evaluating your designs:

Why are users coming to your site? What needs or desires do they have?
How will you ensure that those desires or needs are satisfied?
What assumptions can you make about your users and their skills?
What are the 5 or 10 most important commands or tasks users need to complete?
Are these 5 or 10 actions the clearest and simplest for users to access? (And complete?)
How can users navigate between related areas of your site?
In answering these questions, you'll be forced to make choices about how things are presented, including demoting certain things and emphasizing others. This is the heart of design: making trade-offs around a set of constraints. You can't possibly achieve flow if common activities are as difficult for users to pursue as things they never need. Flow requires focus on the part of the designer.

Flow in Tasks
Once your users are in the right place to do what they want, flow comes into play as an attribute of how much work they need to do to satisfy their goal. Imagine being in a rental car and not being able to figure out where to put the key to start the engine. You'd know you were in the right place for your task, but you'd be frustrated as to how to go about completing it. Your questions would not be about location, but about the steps you need to follow to start the car and drive to the beach. For each task, you can examine the task-level flow by considering the following:

Where does the user start this particular task?
How do they get from one step within the task to another?
What happens if they get lost along the way or make a mistake?
How will they know when they are done?
What common mistakes are they likely to make? How are these handled?
How does the layout or organization of the page make the answers to these questions as self-evident as possible for users?

Flow Deferred
Learning Microsoft® Visual Studio® takes time, as does learning to drive a car, or typing at a keyboard. The design trade-off in these examples is the time investment required versus the long-term payoff for making it. You could make a simpler automobile interface, with one push button for turning left and one for turning right, but it would not provide the level of sophistication needed in order for a driver to successfully navigate the road.So, in some cases, it is acceptable to deliberately delay the point at which users can achieve flow through your design. However, this should only be done with real data and deep consideration about the people you are designing for. Is the investment justified? Do they need that much sophistication? In most cases, developers and designers overestimate the complexity of what people need. When in doubt, strive for simplicity. Only make things complex and involved if you have evidence that it's the righttrade-off.

On the Web, creating learning curves is particularly unreasonable. Users spend most of their time on other Web sites, and the return on investment they would receive for the learning curve required on your site is very low. This is why inventing new kinds of navigation structures or using nonstandard conventions hurts users so much. Notable exceptions justifying additional learning curves include Web applications like Hotmail or online banking, where there is manipulation and storage of data. Because the user needs in these domains are more sophisticated, it follows that the tool to satisfy these needs might need to be more elaborate. They should still be as simple as possible, but are likely to be more complex than your average read-only news Web site.

However, even in cases where a high learning curve is warranted, flow still applies. Training users and helping them through the learning process is actually just a different set of user tasks. You can use the same principles and design approaches for helping users move through the learning process as you do for designing the Web site itself. Avoid the trap of relying on cop-outs, such as "once they learn it, they'll like it." You want to strive for making them enjoy using your design even while they're learning it.

Measuring and Using Flow
For most of the questions I've discussed in this column, there are well-established usability engineering techniques that can provide answers. Cognitive walk-throughs and heuristic evaluations are low-cost ways to see how the parts of your Web site fit together from the user's perspective and will give you a sense of how things flow. Usability studies can be designed to examine these aspects of a design, and provide data about where your current designs fail or succeed. Minimally, you can set goals for your project around these questions, comparing this month's designs to last month's, or your Web site against a competitor's. This won't measure your user's internal sense of flow, which is subjective and difficult to capture, but it does give you an approximation that can be measured, compared, and used to make effective decisions.

Source: http://uiweb.com/issues/issue13.htm

Web Design Tips

Categories
Categories help your visitor move about your site quickly and efficiently. If visitors get frustrated, chances are they will lose interest and find a site easier to navigate. Well defined categories often require a lot of planning and quite a bit of thought, but the time is well spent. Well defined categories may mean the difference between a buyer and someone who just surfs on in frustration.

Be A Site Visitor
In the first case, we mean visit other sites. Note navigation that works, what entices you to look further and what frustrates you to the point of irritation.
Next, we suggest you put yourself in the shoes of your target site visitor. What do you want to find and how do you go about finding it. Pretend a little here, forget that you have ever seen the site before or that you know its content. Really challenge yourself to find what doesn't work well. Look for intuitive ways to find site content. What clues are used to get you where you want to go?
Get opinions from others and then listen well. It's hard to take criticism but you really need people to surf about the site and tell you what does not work for them. When you hear " I couldn't find my way home", don't chalk it up to them being an idiot not able to find their way out of a paper bag. Instead, realize that while clicking on the banner with the logo seemed obvious to you, it wasn't to someone else.

Consistency and Predictability
Sounds pretty boring, doesn't it? We all want to make our site just a tad different and try new things. But listen up! Try your creativity when writing your content, designing your graphics, choosing your colors (but nothing ugly !), customizing your content. Do not try it with your navigation system. Visitors don't like to figure out how to move about a site. Surfers want predictable and consistent navigation, so stick with it and be creative elsewhere. Many want to move about quickly and if you do not allow them to do so, they'll be off in a flash! After all, navigation is not where you want your visitors to focus.
Speaking of navigation, have two different systems with at least one navigation system not dependant on graphics. Not everyone surfs with images on and many sight disabled people do surf the Internet.

Loud Colors Do Not Equal Creativity
Creative design does not mean you should make your visitors pull out their sunglasses or run off to throw-up! Cutting edge design work does not mean using colors no one else would think of using! Nor does it mean showing that you can use every font color available. Believe it or not, cutting edge designs are often so simplistic that others miss the boat with their gee whiz effects and whirling graphics. Unless you are selling graphics, you certainly don't want your graphics and visual effects to down play your content. Images and colors are enhancements, not the main focal point of a site.

Use Technology as a Friend, Not a Distracter
Once again, there is a lot to be said for simplicity and subtlety. New technologies develop every day, but this doesn't mean that you have to incorporate each and every one in your site to demonstrate your abilities. Indeed, some technology is overused. Let's rephrase that - most new technology is over used at the beginning. Everyone wants to show their ability to grasp the latest and greatest and unfortunately, their attempts usually go over board until they lose their fascination of the new look. For example, a bit of Flash is nice in the right place at the right time for the right site. But, be wise, a 4 minute Flash movie feels like an hour and a half on the Internet. Not too many people are going to wait around for it. Don't get me wrong, Flash is cool, but a little Flash goes a long way. More importantly, Flash is just not right for many sites.
In essence you get to experience what every cook has experienced for years - it takes hours to make, but people want to consume it in a very short period of time. Don't try to elongate their experience.
While we are speaking about technology and things going a long way, unless you are a musician or selling music, please opt out of music files. Most of us have a different preference in music. Should we want music while we surf, we play our own. Audio files slow your page loads and irritate many visitors. Some of us surf late at night and don't wish to wake our households to the tunes of Doggy Dog.
Having said that, there are places where music is just the right touch. If you really believe your site is the place (and please think this over long and hard), tune it down with options for increasing volume if necessary and give surfers the chance to opt out quickly.

Image Projection
Face it, great site design really is about understanding and conveying an image, a picture that speaks volumes if you will. Again, I'm going to remind you that the subject matter of the site should be the focus, not your really cool design. Through your words, design, navigation system, colors, graphics and technology, you convey an image. Remember this when you first begin planning your site. Before you decide what the site will look like and what it will contain, ask yourself what is the image you want to convey.
The site you design should leave an impression, a feeling. So what is the impression this particular site needs to convey? Do you want people to laugh? Does the company you are designing for have a conservative image (such as a legal site)? What is the purpose of the site's product or service? If you are designing a site for lumberjacks, leave a subtle impression of wood. Remember, don't scream "wood" with tacky, dark wood paneling, just leave the "feel" of wood with perhaps small graphics of trees and flora, using greens and browns for your site colors and a few small tools used by lumberjacks.
If you are out after a professionalism concept, don't shock your visitors with bright colors, flashy graphics, tons of animation and cartoons. Use fine photographs, subtle colors, simplistic mouse-overs and a conservative layout. Use a compelling writing style void of unsubstantiated claims and "used car salesmanship". Check and recheck your spelling, grammar and punctuation. Provide oodles of knowledgeable content, scholarly articles and links to other professional sites with the same type of content. Avoid banner ads and pop-up windows like the plague.

Repeat Visits
Last but not least, give your visitor a reason to come back. Continually add new content, update your articles, verify site links monthly, offer new contests, newsletters or other content that keeps visitors checking back. Please remember to reward visitors with what they expect (updated content and an ever growing site) when they do return.

Source: http://www.katsueydesignworks.com/designtips.htm

Creating Your Web Design Business Site

If You Don't Have a Site

If you're a Web designer or want to be one and you don't have a site, then you're lucky. You don't have any bad habits and annoying special features to get rid of. But before you race out and start building a site, do some research first. If you haven't written business plan yet, then you should start there.

A business plan will help you to clarify what your site needs and doesn't need.
Look at other designers that are doing similar things to what you do (or want to do):
1. What are they doing with their sites?
2. How do they market themselves?
3. What skills do they showcase (and what do they leave off)?
4. How large is their site?

Once you see what the competition is doing you have a better understanding of what you can do with your own site. But be sure to evaluate any plans you have for your site by the criteria listed below.

If You Do Have a Site

If you already have a Web site, you should be prepared to be ruthless in evaluating it. If possible, get someone else to evaluate it. Look at it with an eye to the criteria set up in your business plan:

1. Does this site show what you offer?
2. Is this site clear and easy to navigate?
3. Are there only a few "bells and whistles"? (As a rule of thumb: if you thought "Wow! Now THAT is cool!" when you built it, it's probably too much for a professional Web site.)
4. Does it include all relevant information, including contact numbers and email addresses, pricing or pricing tiers, services offered, and your qualifications?
5. Does it include a nice, but subdued, portfolio?

Take your time, and think about this project as if you were doing it for a customer. In a way, you are your most important customer. This site needs to draw people to you to generate more business, it shouldn't be something that scares people away or makes it difficult for them to find the information they want.

My Criteria for Judging a High Quality Site

Contact Information For some reason, it is fashionable to make it hard for customers to reach you. Yes, I know, there's problems with spam and so on, but if they can't contact you, how will they be able to tell you they want to hire you for $1Million plus expenses? Be sure your contact information is easy to find on your site, and easy for your customers to use.

Technology Sure, you want to use the latest Flash, PHP, or Java technology. You want to show your clients that you can do what you say you can. But Flash for the sake of Flash is often ugly and just takes a long time to download. Use technology where it makes sense on your site, not just because you can.

Design Use the same professional design techniques you use for your customers' Web sites. You would never put a blinking, flashing red banner ad in the middle of your designs, why are you doing it on your Web site? There is a place for blinking text and flashing graphics, I just haven't found it yet.

Browser Compatibility Do it. Don't force your customers to upgrade to the latest browser, just because you like to use it. If your Web site isn't compatible, they're going to think that's all you can design for, and that's not true, right?

Download Speed It should be fast. If it takes more than 20 seconds to download your site, then it's too big.

If you keep these things in mind while creating a professional site, you'll have a Web designer's Web site you can be proud of.

Source:http://webdesign.about.com

Designing sites for universal access:

The web is a magical place, a place where you can be transported to places you have never before seen. It is growing rapidly, as magical places do, limited only by the imagination of the web site creators. As it continues to grow, users with special needs will increase.

Web site creators will need to rethink their designs to accommodate them. Fortunately, designing a site for visitors with special needs is not difficult and often results in a much cleaner and more usable site. By making a few simple changes to the site web site designers will be able to enjoy visits from people from all walks of life.

What are these special needs likely to be?
1. Visually impaired (blind, color-blind)
2. Deaf
3. Motion impaired; difficulty using a keyboard or mouse
4. Cognitive impairments
5. Text only browsers (Lynx)

Good web design will automatically accommodate many special needs visitors. For example, clearly specifying the purpose of a page and laying out the navigation logically without relying solely on Java-Script, as well as using alt tags for images, would help all visitors. After all, you never know who will be visiting with their graphics turned off because they must pay for every microsecond of time. Or perhaps they will be using an older browser that does not recognize java scripts. Designing accessible sites often means offering two different methods to achieve the same goal.

It helps to understand how people with special needs envision the web. Blind people typically use screen reader software, which reads the page to them one word at a time, row by row. Think about this for a moment. When you first see a web page, your eyes take in the whole layout - the headers, subheaders, side topics, advertisements, etc. You can quickly see the purpose and organization of the page and skip right to the information you need.

People who use screen reader software do not have this advantage. Their. reader. reads. one. word. at. a. time. straight. across. the. page. including. any. alt. tag. information. Think of how confusing top listed links must be! The way to avoid this is to either label your links as links (confusing to the sighted visitor) or use a clear gif with the alt tag information "Navigation bar.

Home Services Articles Portfolio Contact Us Books Resources Your Website

The speech synthesizer will read the alt tag information and then the links. Invisible to the sighted user, this trick is invaluable to those trying to make sense out of a series of seemingly unrelated words being spoken by a speech synthesizer. You could also use a bracketed layout, like this: [link] [link] [link]. The speech synthesizer will read this as, "bracket link bracket bracket link bracket bracket link bracket."

Using ALT text is the primary method of explaining graphics used on the site. If the image is just decoration, use the description "" so the speech synthesizer will ignore it. If the images are links placed next to each other, make sure the ALT text has a trailing space, or is surrounded with brackets. Otherwise, the speech synthesizer will attempt to read all the alt texts as one long word. If the graphics are image maps needed for navigation or information, be sure to label each section with the appropriate ALT text and make sure the information is available in another way as well.

Consider using good sized buttons as the alternate method of access. This provides help to those with motion impairments who can’t click on a small area of a map as well as those that need the visual cues. Page layout and navigation should be consistent on all pages, i.e., always on top or on the left. This will aid visitors using small screens such as telephone devices, as well as visitors with special needs. If your links are going to open a new window or activate a Java-Script, make sure and tell that to your visitors.

Clearly labeled navigation is important to all users, not only those with special needs. While not underlining your links but showing them in a different color looks really cool, it is confusing for new users of the net who are looking for underlined links and impossible to interpret for users who are color-blind or using a black and white display.

Use color carefully. Approximately 8% of web users have difficulty distinguishing colors to some extent. Your colors should not be so dense as to appear black to a black-and-white screen, nor so alike in value as to appear identical to viewers who can’t differentiate between red and green, the most common form of color blindness. The foreground and background colors should contrast sufficiently with each other. Don’t use mystery links. If you need to put your cursor over a link to see where it goes, you are going to not only confuse new users of the web but also make it difficult for visitors with motion impairments. Try to stick with web safe colors - older screen readers have problems with non web safe colors. Web safe colors are easy to identify - the hexadecimal number will be three pairs of matching digits. The only digits you will see in a web safe color are: 00, 33, 66, 99, CC and FF.

A logical navigation layout, besides being good design, is essential for viewers who might be learning disabled, or using a speech synthesizer. A logical design uses HTML tags that identify text for what it is and not just how it looks. For example, headings should be marked up using proper H tags. Speech synthesizers can read this HTML and will give proper emphasis to headings and subheadings if they are marked up with the H attribute. A properly marked up web page can be imported into Word with the headings (H1) and subheadings (H2 etc.) displaying as an outline. Again, a benefit for the visually impaired who may need a quick review of your site. Incidentally, images can be surrounded with H tags if you wish to give the images’ ALT text special emphasis.

Does your site rely on scripts, applets, plug-ins or frames for navigation and/or information? Provide a second way for users to obtain the same information. For example, audio clips should be accompanied by a transcript for the deaf user. Video clips should not be essential to the information presented on the site. If they are, you may want to consider including a hyperlink to an information page which will convey the information in a textual manner. Animated presentations should have an explanatory ALT description for the visually impaired. Don’t make this description too long, however, some speech synthesizers have size limits.

Keep in mind that your text will be read straight across - if you have a picture in the middle of text, the speech synthesizer will read, "text text text picture description text text." It’s often best to align the picture to the right or left of the text so the alt description is read separately. If you really like the look of the surrounded picture, use brackets in your alt description so it will be read as, "text text text bracket picture description bracket text text." Frames are difficult for a speech synthesizer to interpret. If you must design your site in frames, label the top frame clearly with alternate navigational methods.

To assist motion impaired users, navigation options should be clearly labeled and easy to click on. The words "click here" are not the best choice as a motion-impaired user may not be able to hit a target that small. Use descriptive text instead. Avoid the use of the "drop down-box-and-[GO]-button." This is an unnecessary bit of extra clicks even for people without motion impairments.

If you use tables for your layout, keep all the information pertaining to a topic in one cell. Remember that a speech synthesizer will read cells next to each other in sequence. If you have information that is more than one cell long, use shift-enter to keep all the material in the same cell. Avoid very complex tables to display content, if possible. If the table is too complicated, it may confuse the screen reader. If you must use these tables, set short-cut keys and specify the tab order of your elements.

Using bulleted lists are often a good way to present information. Besides being visually attractive and easier to read, numbered lists make it easier for people who are listening to the information. If you use an image as your bullet, be sure to give each image the appropriate ALT text.

Source:http://www.phoebemoon.com/Access.htm

A web site has to be accessible, before it is even usable.

Accessibility refers to the ease with which either disabled users, or users with non-standard browsing situations - or even users with typical visual abilities and the usual browsers - can access the information and other features of a site. In a sense then, accessibility is an extension of 'usability', in that a site needs to be accessible by more than just the CEO at his or her PC on your intranet's T1 or LAN. Consider also blind users, or users at the end of very slow connections, or users with PDAs, etc..

I suspect that most websites are designed with no thought at all for accessibility; in fact many aren't even designed with adequate consideration for usability by anyone outside the site's owners. One very common accessibility issue is the left/right placement of navigation menus - if on the left, text-to-speech is going to read out the whole menu before getting to the actual content (if placed in the first column of a table; there are other solutions, almost never used). On the right, in a second column (as at Web Developer's Virtual Library and EncycloZine) then the user can hear the content up to that point, and then bail out of the page.

We wanted to make EncycloZine highly accessibile - not only for disabled users, but also for users browsing under far less than 'optimal conditions', e.g. small screens or large viewing distance; text mode browsers, etc. So we avoided fixed font sizes and image maps, and we put the navigation menu on the right side rather than the left. A useful way to see how your page looks to these graphics-challenged users is to look at it with a text-mode browser such as Lynx.

Usability refers to the ease with which anyone (disabled or not, or with unusual viewing situations or not) can navigate a site and achieve the objectives which you have set for it, such as learning about your product or about an academic topic, or enjoying the games and puzzles in it, etc. And, beyond that, users should be able to succesfully achieve subsidiary tasks such as filling in forms to order from your catalog, or finding contact information in case they want to let you know about problems with your site (a remarkable number seem to assume that their sites are perfect since they supply no way to contact the webmaster!).

Your web site may be wonderful, but if users find it to be unusable or perceive it to be so then it's unlikely they'll get far enough to discover just what's so wonderful about it. The main considerations for usability are:-

1. do your users possess all the characteristics you assume?

2. the conceptual structure solid, consistent, and intuitive?

3. your users have browsers equipped with the technology you are depending on?

A page of beautifully colored Netscape layer pull-down menus won't be much use to the visually impaired non-English speaking users who favor Lynx, for example. If your target audience profile excludes such people, fine, but very often web sites exclude valid users by default rather than design.

Aesthetics

Web developers have evolved several techniques to get around the deficiencies of HTML's presentation abilities, e.g. complex layout tables; transparent GIF spacers; etc. They're now able to create some very 'cool' looking sites, very popular with the marketing and management types for whom image is of paramount importance. Unfortunately they've all-too often neglected the other important aspects of web site design, such as usability and general user-friendliness.

Aesthetics is clearly important for commercial sites that want to present a good image, but it's a shame when they reveal their attitude to users as 'robots' cast in their own image.
In my experience, the grossest example of an error in web site design, is to emphasise appearance, to the detriment of usability. So many designers seem to feel that aesthetics outweigh everything else - that a web page has to look good, or it's no good. OK, perhaps - but then they go and design the layout down to the last pixel, fixing the font size so it can't be enlarged (in some browsers) and run the text out of the perfectly designed space allocated for it. Never mind that it might be too small for a few people to actually read.

Fixed Font Sizes

Some web designers design the layout down to the last pixel. This means that the font size has to be fixed and unchangeable. If the user changes it, the text won't fill its assigned area, or it will overflow it - design disaster! Never mind that the text was too small to read. It has to look good.
Fixed-font sizes (under IE) can't be resized (in NS they can). There are some sites where the designer apparently wanted such precise control over the layout that they couldn't stand for the text to be resized and thus under- or overflow its assigned box. And they felt that a small font looked best. Now you don't have to be visually impaired to sometimes want a larger font size, for reading comfort.

Some designers apparently cannot grasp that what's perfectly clear to them, on their screens, with their eyes, might not look as fine to others under different conditions... The designer was able to read it perfectly well on his (or her) screen, so what's the problem? Well, we don't all have his (or her) eyes or screen. Perhaps our screen is smaller, or further away. And perhaps we prefer larger text to reduce eye strain and fatigue.

Absolutely fixing font size is probably the best way to insult some of your users. You're insisting that you know best, and that best means "looks good". If I and my cohorts can read it, so can you. Well, my eyesight isn't far from the norm. I wear glasses, but I'm not blind without them. Yet I'm constantly finding web pages where I just want the text a little bigger, but the usual browser controls have no effect. Frankly, I'm saddened that the site designer felt such disrespect for me.

You might expect that once your page "looks good", people will like your site. Sad to say, the "looky-look" crowd have done a great deal of damage to a great many websites. The reason is simple (you'd think): The appearance of a website is only the beginning. A great many that "look good" turn out to be hard to use and poorly organised. For example, one of the commonest mistakes is to insist on rigid layout and font size. Not only are they excluding users with visual impairments, but also users with viewing situations different from the designer's.

You might assume that, to a first approximation, your target audience consists of people not entirely dissimilar to yourself. But beware of treating them as clones. Allow for the possibility that they might be color-blind, or visually impaired, or they might not share your mother-tongue, or they might not have the same kind of computer and monitor as you. Aim for the lowest common denominator first, and field test your prototypes with as wide a variety of "guinea-pigs" as you can muster. Later you can add the 'cool' stuff, continually testing for audience response.

Information Architecture

Web site design properly concerns not only the aesthetics, but also the underlying support structures, and the efforts that go into optimising the user's experience as they interact with the site.

The most general problem is that too many people treat web design as essentially synonymous with graphics design, and don't pay enough attention to the more abstract aspects of usability, such as information architecture. Information architecture concerns classifiying and organising content such that users can navigate comfortably and have the most likelihood of finding relevant topics. My general finding is that shallow hierarchies with rich cross-links work best. Deep hierarchies tend to hide stuff and require too much click-through.

Content First
A general principle of our page design has been "content first, clutter last". Well, maybe not exactly 'clutter' - but stuff like ads and menus are less important to the user than the page content - most of the time. One very important, special user class deserves mention here - search engine spiders. We want to help them figure out what the page is about, and they are guided most by what comes earliest on the page. So the navigation menu is on the right, which also usually lessens the distance a user's mouse has to travel to and from the vertical scroll bar (usually on the right). I think it's also more helpful for blind users who hear the page via screen readers or feel it on braille writers - they don't have to wait for the menu before getting to the content. The problems with left-side margins are:-

1. If the user's window is narrower than the page width, the right side of the page is clipped; the text needs to be moved back into view using the scroll bar. However if it's the navigation menu it's less of an annoyance.

2. Non-graphical browsers (Lynx; HTML-to-speech; etc) will usually render the page text in the order it is presented - i.e. the order it comes out of the file - which is often a substantial amount of navigation stuff. The user will be forced to plow through a bunch of junk before they reach the content.

3. Search engines typically give greater weight to keywords in the earlier part of the page; again, navigation margin contents appear first and skew the results because they relate to other pages than the present one. Also search engine results often display the first part of the page in response to user queries. Navigation menu contents are not much help...

Source:http://kosmoi.com/Computer/Internet/Web/Usability/