About:config Javascript Enable/Disable not working correctly
It used to be that the About:Config Javascript Enable/Disable toggle was an all or nothing swtich. If you turned it off, it was turned off for all of Firefox, including and most importantly active loaded pages with interactive content. It was an absolute need for defense against rouge pages that would do things like trap the close page function and open up many more pages when you closed a page. Other pages would attempt to download code repeatedly and the only way to truly "escape" those pages was to open up a tab with About:Config and toggle the Javascript Enabled option. This is still there, but the behavior has changed in Version 29. It no longer turns off Javascript for all pages loaded or future loaded, only future loaded ones have it turned off. This is a show stopper. Get it back to disabling for all loaded pages or we won't use Firefox anymore.
Todas as respostas (1)
The problem of being trapped in an onbeforeclose event handler was tackled directly. You should not encounter that problem any more as of a few versions ago. (And/or you could use my Escape bookmarklet: http://dev.jeffersonscher.com/bookmarklets.html#escape)
I'm not familiar with the other issue of sites trying to download code repeatedly.
To give feature suggestions, you can use this site: https://input.mozilla.org/feedback
To file a more detailed request for enhancement you can use Bugzilla: https://bugzilla.mozilla.org/