Follow-up r83336, r83460: abandon hardcoded styles altogether, and instead use a...

Follow-up r83336, r83460: abandon hardcoded styles altogether, and instead use a semantic element to pick up appropriate styles which are already in the global stylesheets.  This makes it easier to keep track of where we have implemented this browser-specific tweak in case we have to modify it in future.  By turning debugging on devs have already volunteered themselves to masses of gratuitous extra text-on-page, a few extra elements won't inconvenience them too much further.