So to continue on thy conquest of "List of Best and Worst practices for designing a high traffic website", we're entering the land of Keywords in <alt> tags.
7. Keywords in <alt> tags
Since search engine spiders can't determine what the make up of a image file they use text descriptions to get an idea. These text descriptions are know as <alt> tags. This feature is also used for the visually impaired.
So if I wanted to be sneaky, I could say that the image file with this post was about Technology For Member-Based Organizations or Chamber Software, but the search engines won't want to take my word for it. Since they can't "see" what it is about, I'd have to tag the image with the appropriate text:
<img alt="Alt Tag Knight">
Unfortunately, I'm not trying to get my pages indexed for Alt Tag Knight, so this will do me little good from an SEO perspective. But you can see that since they are picked up by the spiders, it's best for you to tag your images. It's helpful to tag all of your photos if you're striving for 100% validation as well.
Coming up: Keywords in metatags