Google’s massive databases come from its tiny minions “crawling” the web, traversing links and storing page views. They are called “spiders,” and for your site to get a good search rank from Google (and MSN, and Yahoo, etc… each of which has their own spiders), you need to know a little bit about what they are and how they work.
This is by no means a comprehensive explanation of spiders or seo methods. Volumes are being written about those topics. This is just a basic introduction to spiders and accessability on the web.
References
Spiders
First of all, spiders are not people. They are programs run from Google’s servers that view your websites in a stripped-down, text-only virtual browser. Second, unlike your house, having your website crawling with spiders can be a very good thing.
Black Dog’s home page might look a little like this when viewed by a spider:

This is a screenshot of a text-only view of blackdogdev.com’s homepage. As you can see, the big photo of an adorable dog is gone; so is our nice-looking logo. All that remains is the most important part: the content. The text is the only thing the spiders care about.
Accessability
A spider can’t tell the difference between a photo of your dog and a photo of a fire engine, unless there is text available to give it meaning. Typically, this is achieved using an image’s alt attribute.
On blackdogdev.com, the alt text on the big dog photo is not very specific: “Loading Image…” doesn’t really mean anything. The logo, however, is better. Its alt text is “Black Dog Studios”. Much more relevant!
These alt attributes aren’t just for search engines. They are also used by screen-readers for the blind, who cannot see the screen at all but still take advantage of the wealth of knowledge on the net. For the images on your site to be meaningful to the blind or to spiders, they must have descriptive alt tags: “Portrait of Henry Flagler, January 2, 1830 – May 20, 1913” rather than “H_Flagler”. alt tags should never be left blank.
Remember: if you can’t navigate your site without graphics or flash, then spiders and the disabled can’t either. If you don’t like what you see when your site is stripped down to just text, a structural redesign may be in order.
Tools
See this blog entry in a text-only browser.
To see your site like Google does, you can use any of the available text-based browsers out there. A short list includes: