How to achieve Web standards and quality on your Web site?

W3C QA - How to achieve Web standards and quality on your Web site?: "Here you will find easy, painless techniques and ideas to improve your Web site quality and make your Web site valid. This document is intended for HTML users, developers working on Web applications, and Web masters.

Most of the Web sites on the Web are not valid. We may assume that this is the case for 99% of the Web pages, but there are no statistics to support this. It would be interesting to run a survey to prove that this case is indeed true."