Root can not open display

[Dave_Bechtel]

1. Try using " sudo nedit " instead, sudo will pass the $DISPLAY variable for you

2. If already su'd to root, try ' nedit -display :0 '.

I login as a normal user, then su to root, can not open any graphic program, like nedit, etc, always get:

NEdit: Can't open display

Please help.
Thanks,