Rated 5 out of 5 stars

This is a great addon if you are trying to keep your HTML codes valid and tidy. It works also for your offline HTML pages, which means you can make your corrections before you publish your pages. Also as far as I undertstand it this means that it does not intrude on your privacy like Total Validator (which sends the URLs somewhere for inspection before giving you the results). It has two systems of validation, one is the one used by W3C (SGML Parsel) and the other is HTML Tidy, which as far as I understand is unique to this addon and it gives you different corrections than W3C.

This review is for a previous version of the add-on (