screen size ...

[B. Marchand]

this should be an easy question. I noticed that when I run startx the 
server defaults allow the screen to extend beyond the limits of the 
physical display. So, if I push the mouse against the edge of the screen 
I pan into a different section of the display. How can I turn this off? 
I just want the limits of my display to be the same as the physical 
dimensions of my LCD.

--B.