VALIDATOR.UNL.EDU

The Nu Html Checker (v.Nu) is an ongoing experiment in better HTML checking, and its behavior remains subject to change. In particular, because new types of error checks continue to be actively added to the checker, there is no guarantee provided that if the checker reports zero errors for a particular document at one point in time, it will report zero errors for that same document at some later point in time... Steve Faulkner has created the following bookmarklets you can use in conjunction with the Nu Html Checker... Check serialized DOM of current page: grabs the serialized DOM of whatever page you're currently browsing and sends it to the checker