JSLint (prior to version 2013-03-18) throws the "Currently, ADsafe does not operate on whole HTML documents. It operates on <div> fragments and .js files" error when the adsafe and fragment options are set to true (they're false by default) and you pass it an HTML fragment that contains an <html> tag before the opening ADsafe widget <div> tag. Here's an example:
In a commit on 20th March 2013, HTML, CSS and ADsafe parsing functionality was removed from JSLint. If you rely upon this functionality, you will be unable to upgrade JSLint to a version beyond that date.