Validity

Validity is a small Google Chrome extension to validate the HTML content on a website simply by clicking on the small icon that appears to the right of the search bar.

A little less than five seconds after your click, the application will show you validation errors and tell you how many there are. To see them, you'll need access the Javascript console (in Google Chrome tools).

Validity is a very interesting tool to help you check the quality of the HTML on any website in a matter of seconds.