Google's website Design and content guidelines

Following Guidelines should be considered when developing any web site. These points are directed by Google. These points are your Guide to Professional Website Design and Development

Google's Design and content guidelines

1. Make a site with a clear hierarchy and text links. Every page should be reachable from at least one static text link.

2. Offer a site map to your users with links that point to the important parts of your site. If the site map is larger than 100 or so links, you may want to break the site map into separate pages.
3. Create a useful, information-rich site, and write pages that clearly and accurately describe your content.
4. Think about the words users would type to find your pages, and make sure that your site actually includes those words within it.
5. Try to use text instead of images to display important names, content, or links. The Google crawler doesn't recognize text contained in images.
6. Make sure that your TITLE tags and ALT attributes are descriptive and accurate.
Check for broken links and correct HTML.
7. If you decide to use dynamic pages (i.e., the URL contains a "?" character), be aware that not every search engine spider crawls dynamic pages as well as static pages. It helps to keep the parameters short and the number of them few.
Keep the links on a given page to a reasonable number (fewer than 100).

Source : http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=35769