The official W3C validator is a great place for checking if our website's HTML/XHTML is standards compliant. However, it can validate a single URL at a time.

W3Clove is a free to use web service which crawls any given website to generate the sitemap of it (or accepts sitemaps directly) and validates each URL through the W3C's validator.

The errors and warnings for each URL is stored and displayed as a list. And, it compiles a basic report of the most common errors and warnings as a summary.

W3Clove also remembers the recent checks you have made and present them to you quickly.

Styled Menus is a website presenting various free CSS menus.

Menus provided are cross-browser compatible & W3C validated.

There are currently 20 menus & new ones added regularly.

It is a handy resource to directly use them or to get inspired.

Free Site Validator is a very handy free service for validating webpages.

When compared to W3C validation services, this solution scans not only 1 page but follows links, goes deeper & almost scans all webpages in a website.

The service uses W3C validation service at the backend & enables you to scan multiple websites.

Report generation can take some time considering it scans all webpages but the service can simply notify you when the validation is completed.

Validationicons.com is presenting free W3C validation icons that are used to show that the website validates with the related guidelines.

There are 2 download packages offered:

• Basic package: 20 GIF / PNG  icons in #505050 color
• Dev package: Full editable PSD pack

P.S. If you’re planning to create your own icons using the PSD pack, here are the W3C guidelines for the icons.