By: Trenton Moss

October 19th, 2004

Reader Rating: 8.5

One of the main benefits of Web accessibility is that a Website that's more accessible to people is also usually more accessible to search engines. The more accessible your site is to search engines, the more confidently they can guess what the site's about, giving your site a better chance at the top spot in the search engine rankings.

Not all of the accessibility guidelines will help with your search engine rankings, but there are certainly numerous areas of overlap. Let's look at each in turn.

1. Assign ALT Descriptions to Images

Screen readers, which are used by many visually impaired Web users, can't understand images. To ensure accessibility, an alternative description needs to be assigned to every image; the screen reader will read out this alternative, or ALT, description:

<img src="filename.gif" alt="image description goes here" />

Like screen readers, search engines are commonly assumed to be unable to understand images. But some search engines index ALT text. By assigning ALT text to your images, those engines will be able to understand even your pictorial content.

Of course, numerous search engines don't take any notice of ALT text. The proliferation of ALT tag spamming undermined the relevance of ALT text in the eyes of these engines, which no longer consider it in their relevance algorithms.

So, why bother with image ALT text? Because your rankings may improve in search engines that do take it into account, and make your site more accessible.

2. Display Text Through HTML, Not Images

Text embedded in images appears pixelated, blurry, and is often unreadable by those who use screen magnifiers. From an accessibility point of view, text embedded in images should therefore be avoided.

It seems that at present, search engines are also unable to read text embedded in images. Well, you can just apply ALT text to those images, right? Unfortunately, there's strong evidence to suggest that search engines assign less importance to ALT text than they do to regular text. Why? Spammers (again!), as explained above.

The answer? To ensure that your site is accessible and your content counts as much as possible toward your search ranking, avoid embedding text in images.

3. Use Descriptive Link Text

Visually impaired Web users can scan Web pages by tabbing from link to link, listening to the content of the link text as they go. As such, the link text in an accessible Website must always be descriptive of its destination.

Search engines are generally seen to place importance on link text, too. Many engines assume that link text will be descriptive of its destination, so they examine the text of all the links that point to a given page. For instance, if all the links pointing to a page about widgets read, 'click here', search engines can't gain any information about that page without visiting it. If, on the other hand, all the links say, 'widgets' then search engines can easily guess what the linked page is about.

One of the best examples of this technique in action is for the search term, 'miserable failure'. So many people have linked to George Bush's bio using this phrase as the link text, that now when the words "miserable failure" are searched on Google [1], George Bush's bio appears top of the search rankings!

4. Website Functions with JavaScript Disabled

JavaScript is unsupported by about 7% of Web users [2], either because they've turned it off (perhaps to prevent pop-up adverts) or because their browser doesn't support it. Many forms of JavaScript aren't accessible to those who use screen readers.

It's accepted that few, if any, search engines can understand JavaScript -- these services will likely be unable to index any JavaScript-driven content. Perhaps more importantly, they'll also be unable to follow JavaScript-driven links. You may really like the look of your dropdown menu, but search engines won't if they can't access certain pages on your site because of a lack of regular <a href> links.

5. Alternatives to Flash-Based Content Provided

Like JavaScript, Flash isn't accessible to many users, including those using screen readers. Equally, few search engines can access Flash -- be sure to provide equivalents.

6. Transcripts Available for Audio

Hearing impaired users obviously require written equivalents for audio content in order to access that information. Typically, search engines are also unable to access audio content; transcripts provide them relevant text to index.

7. Site Map Provided

Site maps can be a useful tool for visually impaired users as they provide a straightforward list of links to the main pages on the site.

Site maps are also great for search engines as most search engines can instantly index your entire site once they arrive at the site map. Next to each link you might also provide a short keyword-rich preview of the page, to improve both the user experience and potential search ranking. All links should, of course, be made through regular HTML, not JavaScript (see point 4 above).

8. Meaningful Page Title

When we arrive at Web pages, the first thing that appears -- the first thing that visually impaired users hear -- is the page title. Visually impaired Web users don't have the privilege of being able to quickly scan the page to see if it contains the information they're after, so it's essential that the page title effectively describes the page content [3].

If you know anything about search engine optimisation you'll know that the page title is among the most important attributes on the page. If it adequately describes the content of that page, more search engines will be able to more accurately interpret what that page is about.

9. Headings and Sub-Headings Used

Visually impaired Web users can scan Web pages by tabbing from heading to heading, as well as from link to link (see point 3 above). As such, it's important from an accessibility standpoint to make sure your headings are correctly marked up using <h1>, <h2>, etc. tags.

As a general rule, most search engines will assume that the text contained in heading tags is more important than the rest of the document's text, as headings describe the content immediately below them. Search engines assign the greatest importance to <h1>, then <h2>, and so on. Make sure you use the heading tags properly. Don't abuse them -- the more text you have contained between heading tags, for example, the less importance search engines may assign them.

10. CSS Used for Layout

Screen readers can more effectively work through the HTML code of CSS-based sites as there's a greater ratio of content to code. Websites using CSS for layout can also be made accessible to in-car browsers, WebTV and PDAs. As I mentioned in the first part of this article [4], it's estimated that 58 million PDAs will be sold worldwide in 2008 [5].

Search engines tend to rate CSS-based sites higher in search rankings because:

• The code is cleaner and therefore more accessible to search engines
• Important content can be placed at the top of the HTML document
• There is a greater density of content compared to coding

An example of the value of CSS in action is the Juicy Studio site [6], which recently changed from a regular table-based site to a CSS-based one. Traffic to the site has since increased six-fold.

Conclusion

With the overlap between Web accessibility and search engine optimisation there's no reason not to implement basic accessibility techniques on your Website. SEO concerns never provide a viable excuse for disregarding accessible Web design methodology.

The application of accessible coding methods to site design in no way hinders a search engine's perception of your site, and in many cases greatly improves access to your content. The implementation of accessibility techniques might just give you a better chance to gain higher search engine rankings and, thereby, attract more visitors.

[1] http://www.google.com/search?sourceid=navclient&ie=UTF-8&oe=UTF-8&q=miserable+failure
[2] http://www.thecounter.com/stats/2004/July/javas.php
[3] http://www.sitepoint.com/article/html-title
[4] http://www.sitepoint.com/article/accessible-usable-website
[5] http://www.etforecasts.com/pr/pr0603.htm
[6] http://www.juicystudio.com/