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, George Bush’s bio appears top of the search rankings!
<a href> links.
5. Alternatives to Flash-Based Content Provided
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.
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.
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
<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, it's estimated that 58 million PDAs will be sold worldwide in 2008.
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, which recently changed from a regular table-based site to a CSS-based one. Traffic to the site has since increased six-fold.
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.