Search engines guidelines

A webmaster should always follow acceptability guidelines for each search engine. Review these guidelines and become familiar with them.

Google Guidelines:
http://www.google.com/Webmasters/guidelines.html

Yahoo Guidelines:
http://help.yahoo.com/help/us/ysearch/basics/basics-18.html

Ask Guidelines:
http://about.ask.com/en/docs/about/editorial_guidelines.shtml

DMOZ Guidelines:
http://www.dmoz.org/help/submit.html

Coding guidelines published by the World Wide Web Consortium (://www.w3.org/) should be followed as well as tested using their free valuator which checks the markup validity of Web documents in HTML, XHTML, SMIL, MathML, etc. (://validator.w3.org/)