if using Vim in GNU Screen and you want to use fancy key bindings to
navigate tabs, first make sure the below is set in your .vimrc file

set term=xterm

this will allow Ctrl+PageUp/Down to work to switch tabs

if you want to use Alt+Up/Down add the below in

map <M-up> :tabprevious<CR> 
map <M-down> :tabnext<CR>

for a simple way to switch between GNU Screen 'screens' using Alt +
Arrow key, use the below key bindings in your .screenrc file

 
# Arrow keys to switch terminals (only works with X) 
# Alt + left 
bindkey ^[[1;3D prev 
# Alt + right 
bindkey ^[[1;3C next 

note:
- not use Ctrl + Alt + Left/Rigth Arrow as its used by GNOME to swap
virtual desktops
- nor firefox style as its used by GNOME Terminal for switching its tabs
- to find out what Alt/Fn/Ctrl characters equal what just execute cat
and start typing