Videos
I am the author of the Firefox extension. I have recently rewritten it for Chrome and the new Webextension API of Firefox.
See more info on the extension homepage:
http://users.skynet.be/mgueury/mozilla/index.html
The direct link from the Google Chrome store is this:
https://chrome.google.com/webstore/detail/html-validator/mpbelhhnfhfjnaehkcnnaknldmnocglk
Enjoy,
There is a new HTML validator available for Chrome. It uses a JavaScript port of LibTidy and thus validates locally without the need of remote services.
See https://chrome.google.com/webstore/detail/anjdemaoejlpgmnmkijdemoiebcddhkc
W3C Markup Validation Service: This is a well-known and widely used tool for validating HTML markup. It's available as a web service, and you can also download the source code and host it on your local environment. It can validate individual pages or entire websites by submitting a sitemap or list of URLs.
Visit https://validator.w3.org/
These days you likely want something like html-validator for a specific programming language, in this case Javascript, configured to scan output HTML/CSS files and hooked into CI for automated validation.
Unless of course there's some user input that can result in different HTML which would normally not be checked. In that case you can generate special test output just for tests and cover all the cases that need to be covered. Might not work for your website depending on what it is and what exactly you need to verify, but I'm mentioning it as the most optimal possibility for lots of more basic sites.