Using the same style as the notification for Undo in bug 722234, we should let users enable caching from the new tab page since thumbnails will not work without caching enabled. The text could be: (Enable the cache to show thumbnails? _Enable cache_ _Learn more_ _x_) Where _x_ dismisses the notification. This would enable the browser.cache.disk.enable pref, which can get disabled in multiple ways and forgotten about, including the use of Firebug where the cache can be disabled.

Sounds like a good idea. This is likely a edge case as cache'ing is on by default. The "enable cache" ideally would also be linked directly to the pref panel.

Lower priority for now given the use case.

I like the suggestions, but we won't need this anymore with bug 744388 fixed.

Fixed by bug 744388.