I think I used to press Ctrl+Shift+PageUp and Ctrl+Shift+PageDown when I started to use tabbing in Gnome Terminal or Gedit if I recall correctly.

I think Firefox did support such keys for some time, but I could be wrong. Chromium supports them. If you are a mouse person, you probably think this is not important. But if you also use multi-profile at the same time, i.e. using --no-remote for other profiles. The drag and drop for bookmarks or tabs doesnt work for those browser processes with no-remote, which causes you can not drag a tab handler to re-order tabs, hence you need another way to re-order.

Using Vimperator proves thats a great advantage once again. By adding the following lines to ~/.vimperatorrc:

map <C-S-PageUp> :tabm -1<CR>
map <C-S-PageDown> :tabm +1<CR>

I can use those keys to move a tab.

If you prefer JavaScript version, you can use:

map <C-S-PageUp> :js getBrowser().moveTabBackward()<CR>
map <C-S-PageDown> :js getBrowser().moveTabForward()<CR>

They work less perfect than Vimperator built-in command :tabm[ove] when the tab is the leftmost or rightmost tab and it also steals focus for tab handler.