I frequently type :E (uppercase) instead of :e (lowercase) when I wish to open a file. Same goes for the mappings of :w[a] and :q[a].
I thought I could fix that with the following in my .vimrc:
cnoremap E e
cnoremap W w
...
They work by transforming the E into e, but sadly it also makes it harder to open/save a file with an uppercase E, the latter gets transformed to lowercase on the fly. To get the uppercase letter I know have to ctrl-v <letter> in C-mode
Is there a better method to help me with my common typos?