xscreensaver: Can't open display: :0.0

[yonas abraham]

I am getting the ff error on xscreenaver

xscreensaver: Can't open display: :0.0
xscreensaver: running as yonas/yonas (500/500)
 
xscreensaver: Errors at startup are usually authorization problems.
              But you're not logging in as root (good!) so something
              else must be wrong.  Did you read the manual and the FAQ?