Everyone has to use Flash and PDF content at some point. Wait...no you don't. Stay away from Flash and PDF content. While some modern search engines can index the content, the effectiveness of indexing large quantities of Flash and PDF content is suspect. PDF content should always open in a new browser window, making this content slightly more difficult for your users to manage. Why not make it easier for everyone. While it is still easier to animate some effects in Flash, many animations can be
AJAXified. Take a look at Alighten's
SEO friendly banners for an example of how to avoid Flash content.