Now that the problematic site has been blocked from running scripts, it will no longer cause unresponsive script warnings. Other causes. An add-on could be causing the problem. See Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems. Based on information from Unresponsive Script Warning (mozillaZine KB). May 22, · @jayp: Just mentioning. XHTML doctype is still HTML parser. You have to sent content as application/xhtml+xml to run it in XHTML parser (like XHTML specification says). There is whole a lot of content which claims to be XHTML, but sends normal HTML doctype. Apr 02, · Also, if the problem only happens on one or two Web pages, it might be a problem with those pages. If you decide to ignore the errors, you can disable script debugging. Note If this problem occurs on more than one or two sites, do not disable script debugging.