In OSX Lion, in vim, I try use this nnoremap.
nnoremap <m-Down> :cnext<cr>zvzz nnoremap <m-Up> :cprevious<cr>zvzz
I added the nnoremap to ~/.vimrc, but when I press
ALT-Down nothing happening.
If you are using Vim in Terminal.app, the Alt key doesn't work by default. You must enable it in its preferences, it's a checkbox labeled "Use option as meta key" in the settings panel.
But you could use MacVim which understands the Alt key by default.
But you could use