The Alt-<number> keyboard shortcut is used to switch between tabs. However, the key event used to switch a tab seems to also propagate down to the content itself. This creates weird interactions: - I switch to third tab - The web page running in the third tab actually uses Alt-3 to do something - After switching tabs the web page does something unexpected because the browser chrome didn't swallow the event during its tab-switching procedure. The most irritating candidate seems to be XenForo forum software that uses Alt-<number> to go to different sections in its menubar. For example, alt-4 seems to open a search page and going there provides no new entry in the browser history. So, if I've tab-opened the forum to display new posts and then later I switch to it using Alt-4, it makes the content go to its search panel with no way to go back to new posts. Ironically, switching _away_ from the tab 4 does not register to the content so I can't even use the forum's own keyboard shortcuts to navigate back to new posts section or any other section. Having the forum in tab X will only ever let the forum see Alt-X and nothing else. This all stems from the fact that Firefox lets the initial tab-switching key event through whereas I think it shouldn't. It maybe should if the corresponding tab is already active but it certainly shouldn't when a tab-switch actually occurs. I've obviously disabled the content's capability to override keyboard shortcuts but it doesn't help in this because the content is not overriding anything: it seems to be just listening to a keyboard event that it shouldn't see. Did I miss some option in about:config or do others see this as well?