See Your Site With the Eyes of a Spider

Making efforts to optimize a site is great but what counts is how search engines see your efforts. While even the most careful optimization does not guarantee tops position in search results, if your site does not follow basic SEO truths, then it is more than certain that this site will not score well with search engines. One way to check in advance how your SEO efforts are seen by search engines is to use a search engine simulator.
Spiders Explained

Basically all search engine spiders function on the same principle – they crawl the Web and index pages, which are stored in a database and later use various algorithms to determine page ranking, relevancy, etc of the collected pages. While the algorithms of calculating ranking and relevancy widely differ among search engines, the way they index sites is more or less uniform and it is very important that you know what spiders are interested in and what they neglect.

Search engine spiders are robots and they do not read your pages the way a human does. Instead, they tend to see only particular stuff and are blind for many extras (Flash, JavaScript) that are intended for humans. Since spiders determine if humans will find your site, it is worth to consider what spiders like and what don't.
Flash, JavaScript, Image Text or Frames?!

Flash, JavaScript and image text are NOT visible to search engines. Frames are a real disaster in terms of SEO ranking. All of them might be great in terms of design and usability but for search engines they are absolutely wrong. An incredible mistake one can make is to have a Flash intro page (frames or no frames, this will hardly make the situation worse) with the keywords buried in the animation. Check with the Search Engine Spider Simulator tool a page with Flash and images (and preferably no text or inbound or outbound hyperlinks) and you will see that to search engines this page appears almost blank.

Running your site through this simulator will show you more than the fact that Flash and JavaScript are not SEO favorites. In a way, spiders are like text browsers and they don't see anything that is not a piece of text. So having an image with text in it means nothing to a spider and it will ignore it. A workaround (recommended as a SEO best practice) is to include meaningful description of the image in the ALT attribute of the tag but be careful not to use too many keywords in it because you risk penalties for keyword stuffing. ALT attribute is especially essential, when you use links rather than text for links. You can use ALT text for describing what a Flash movie is about but again, be careful not to trespass the line between optimization and over-optimization.