Thats aggravating isn't it? I've done that before too.
Well, here is a suggested way out for you:
1. once booted up and the display is either black-on-black, or showing skewed colors at a diagonal, or just text-mode errors.. change to a clean text-mode tty by pressing <Ctl><Alt><F2> and a new login should appear.
2. login and, go back over to /etc/X11 and edit the file "xorg.conf" to fix your mistake and save the file.
3. go back to the fouled up graphical screen via <Ctl><Alt><F7> and attempt to restart it by pressing <Ctl><Alt><Bksp>. If that resets the graphical mode and puts up a graphical login screen, you are done.
4. If the <Ctl><Alt><Bksp> has no corrective effect, you may have to reboot.
5. In the future, practise defensive programming by making a backup copy of the file BEFORE editing and changing it. Also, select more that one graphical resolution so that if one is bad, you can simply cycle on to the next one by pressing <Ctl><Alt><+> or <Ctl><Alt><->
In xorg.conf in the "Section screen" use a Modes line like this:
Viewport 0 0
Modes "1600x1200" "1280x1024" "1152x864" "1024x768" "800x600" "640x480"
That way, if 1600x1200 fails at startup, by cycling forward, you can get the X server to try mode 1280x1024 and so on.
Linux Counter # 52009