User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:8.0) Gecko/20100101 Firefox/8.0 Build ID: 20111104165243 Steps to reproduce: "stuff stuff stuff <!--[if IE 6]> stuff stuff stuff" will display as "<!--[if IE 6]>" being the comment and the rest being normal source code, but only if the HTML comment never actually gets ended. I.e. stuff stuff stuff <!--[if IE 6]> stuff stuff stuff--> would display correctly. So this normally isn't an issue but is somewhat bothersome when trying to find your error. Actual results: thinks "<!--[if IE 6]>" is the html comment Expected results: should have thought "<!--[if IE 6]> stuff stuff stuff" is the html comment. Again this only works with malformed comment tags, if there is a proper end at some point, i.e. "-->", it'll behave normally

There will be a completely new parser used for View source in Firefox 10 (implemented in bug 482921). Can you see how that one behaves?