The bothering prompt when a web app is using offline application cache (a.k.a appcache) has been removed from Firefox!
Beginning with Firefox 26 there will no more be this prompt users have to accept. Firefox will cache the stuff automatically as if the user has clicked the Allow button.
This actually applies to every software based on Gecko, like Firefox Mobile or Firefox OS. Tracked in bug 892488.
Application cache, a not really favorite feature, is not that widely used on today web and one of the reasons has been this prompt. It may be a little late in the game, but it still has happen. I’m curious on what the feedback from web developers is going to be.