The search engines spider and index Web sites and they do so primarily according to links found on each Web site and spiced up with clever algorithms. Therefore, it is important to design and organize Web sites with that fact in mind. Making it easier for search engines to retrieve Web site's content should be a priority for all Webmasters.
Long time ago it was not considered important to design search-engine-friendly Web sites and there are Web sites still out there that are designed primarily with technology that basically prevents search engines from easily spider Web sites.
The save way of making a Web site search-engine-spider-friendly is to ensure the spiders can follow links on a Web page. It is as simple as that, a plain common sense. The search engine spiders can index almost any type of links be it a dynamic link or static HTML link.
A new technology recently introduced by one of the major search engines provides a way to help its spiders understand SWF and Flash files to make it easier to spider Web sites powered with these rich Internet applications (RIA) and animated presenations.