[tacotime]

Triple shift pops up a red "Access Denied" message in the middle of the screen. Alt just shifts focus to the browser's toolbar, at least in Chrome.

[pjerem]

Alt alt alt should show a big green Access Granted :)

[beeboobaa3]

It just opens/closes the file/edit/view menu.

[extraduder_ire]

If you press it enough times, eventually three alt keys will get through to the page and it will pop up. I think it could could prevent the menu appearing by using preventDefault() on the keydown event.