There are also sites that provide tools to aid in the effective web design process, try some of the following:

• Netmechanic
  Tools to improve and promote your site, including a free test of 5 pages to discover broken links, spot bad HTML code, check browser compatibility, find slow-loading pages, and check your spelling.
• Useable Net
  Lift Evaluation software, on which you can have a free test of 5 pages, automating the process for creating usable and accessible content as you go.
  
• Delorie Software
  Tests for backwards compatibility; for instance if a site would still function in HTML 2.0; how it would look in a Lynx viewer.
• PurePromotion
  Analyse the metatags on your site
• Webtime Internet Tools