=W3CValidate(string pageUrl) : string
Validates the HTML of a page using W3C validation service and reports number of errors and warnings.
W3CValidate("http://google.com") => "37 Errors, 2 Warnings"
Note that this is using W3C API and missure (massive amounts of validations) can lead to your IP beeing blocked by W3C. 1000ms sleep between validations has been added to avoid this.