- alt+[letter] hotkeys just register as plain [letter] presses
- control+n and control+t open new window and tab respectively.
*alt+[letter] hotkeys should not bubble to the browser level and should be captured by JS instead - it was definitely possible to reserve these with JS and prevent from bubbling to the browser in prior FF versions (Chromium, for reference, allows JS scripts to capture pretty much all of the alt+[letter] keys).
- control+n and +t not being bindable may be expected behaviour, but for me at least Chromium doesn't seem to allow JS to block this.
Am not sure if there's a JS hack that would make some of these functions work again, but as it stands, the lack of alt+[letter] access this has broken some web-apps in Firefox that have bound hotkeys to access their own menus or other functionality, for example.