It makes me sad every time I try a Vim with a non-zero 'scrolloff' setting. Since I started using Vim I have learned to use H and L efficiently when navigating, but non-zero 'scrolloff' changes where H and L move the cursor to - and somehow non-zero 'scrolloff' is now the default in Ubuntu if a user hasn't created a vimrc file (even an empty file will do).

Note that this seems to work much better in Chrome than in Firefox - when I press Ctrl in Firefox, it activates Visual Block mode (so e.g. Ctrl-D, Ctrl-U, Ctrl-O, Ctrl-I won't work).