(X)HTML5 Checker

Add-on to validate the tab's html using https://validator.w3.org/ web service APIs.

- It can be used while developing the website to check for errors and maintain standards in your code.
- It sends the current webpage’s HTML to the https://validator.w3.org/nu/ web service in order to check it for errors.
- You can detect all the errors, in a popup list, to facilitate the refactoring of the code, the error part is highlighted and the source code is also displayed where the error is found.