Search Engine Optimisation and Accessibility: "The following chapters describe how search engines algorithms, and attempts to address them through search engine optimisation as marketing technique creates new opportunities for making web content accessible - and equally, how improving the accessibility of a site can help maximise both it's search engine promotion potential and increase user conversions and ROI."
Main points:
Provide a text equivalent for every non-text element (e.g., via "alt", "longdesc", or in element content). This includes: images, graphical representations of text (including symbols), image map regions, animations (e.g., animated GIFs), applets and programmatic objects, ASCII art, frames, scripts, images used as list bullets, spacers, graphical buttons, sounds (played with or without user interaction), stand-alone audio files, audio tracks of video, and video.
Ensure that dynamic content is accessible or provide an alternative presentation or page. Until user agents can automatically read aloud the text equivalent of a visual track, provide an auditory description of the important information of the visual track of a multimedia presentation.
Until user agents render text equivalents for client-side image map links, provide redundant text links for each active region of a client-side image map.
Ensure that all information conveyed with colour is also interpretable without colour, for example from context or mark-up.
Ensure that foreground and background colour combinations provide sufficient contrast when viewed by someone having colour deficits or when viewed on a black and white screen.
Search engine optimisation techniques make good use of the separation of content and presentation. One approach that shows excellent results in search engine optimisation campaigns is the use of layouts controlled by Cascading Style Sheets (CSS). However, organize documents so they may be read without style sheets. For example, when an HTML document is rendered without associated style sheets, it must still be possible to read the document.
For data tables, identify row and column headers. For example, a table that lists UK tour businesses may have, as column header, "Tour operators". If this cell is not differentiated from others, then it is simply one phrase amongst many. However, if the cell is marked as a column header, this clearly communicates to search engines that this page is a resource about "Tour operators" and not just a page that mentions the phrase incidentally. As such, this makes it a powerful search engine promotion tool for describing structured data.
Provide summaries for tables. The CAPTION element and the "summary" attribute are intended to describe the purpose and content of a table. This is particularly useful when a table's content can only be properly understood visually rather than semantically.
Ensure that pages are usable when scripts, applets, or other programmatic objects are turned off or not supported. If this is not possible, provide equivalent information on an alternative accessible page.
Frames are essentially deprecated and search engine promotion professionals will advise against their use for solid optimisation reasons. However, if frames must be used then the best available SEO strategy available is to enrich the frameset with descriptive content for search engines through the TITLE tag and the content of the NOFRAME element.
Do not to use link text such as "click here", "read more" or similar variants. Using anchor text, (sometimes called link text) to accurately and specifically describe the page to which it links is a cornerstone of effective search engine optimisation.
Provide information about the general layout of a site (e.g., a site map or table of contents).
Conclusion
It seems unlikely that all accessibility guidelines can or will be included in search engine algorithms. There is, however, a clear tendency that accessibility as a whole will be factored in more strongly in the near future, and some guidelines will almost certainly be considered for inclusion.
Since, it is impossible to second guess which they will be, the sensible, no-risk strategy is to improve accessibility across the board.
This article has been based on the Search Engine Optimisation and Accessibility guide. A free PDF version is also available.
posted by Jen @ 8:20 AM
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