If the site has been designed to comply with basic W3 accessibility standards, then it has passed the first hurdle. “Frames" are a no no. Most Flash based sites (without underlying text alternative) are a no no. Text built into graphics (without underlying text alternative) is a no no. Each of these factors makes it nigh on impossible for the search engines to see what is there in the site and to navigate and “crawl' your site content. Flash may be good for design, but it is often slow and is search-engine-robot unfriendly.
Another problem area for search engines is sites that are based on “frames" techniques. This approach was popular a few years ago but is now to be strongly discouraged. Search engines cannot easily cope with the internal links and page identifiers - so avoid them. So, in summary,
- Rule #1 Make sure your site is built to at least AA accessibility standards. How can you test this? There are tools available on the Web, but for a basic assessment install the Mozilla Firefox browser - we recommend this over MS IE8 and go on the tool bar to View>Page Style>No style. If everything reads beautifully logically from the top of the page downwards (not in columns or interrupted by graphics) then this is what a blind person could be hearing. Imagine listening to the page being read to you - is the site still easily navigable? Do the images have captions? Search engine robots have a similar approach. Make sure the un-styled page doesn't annoy or confuse! The search engine sees things likewise!