I think this is a recent behavior change (that I'm tempted to call a regression). Steps to reproduce: 1. Press cmd+t 2. Type a url (with the help of the awesomebar completion) 3. press enter to load it. Actual result: The 'back' button is enabled, and clicking it sends me to about:newtab Expected result: The 'back' button should be disabled, as I've never used the about:newtab page to get there. Note: it makes sense to enable going back to about:newtab when the user loaded the current page by clicking on a tile in about:newtab, but in the case above where I interacted only with the keyboard and the awesomebar I haven't even noticed the stuff in the about:newtab page, so having it in the history is surprising/confusing.