Maybe a button as an alternate for ctrl+/? Doesn't seem to work with a non-US (Norwegian) keyboard layout? (Iceweasel/Firefixo 23.0 Debian Wheezy - note also noscript and vimperator -- which can make keyboard navigation tricky).

Doesn't seem to work in chromium (Chromium 29.0.1547.57 Debian 7.1) either, with Norwegian keyboard layout.