Wednesday, 1 March 2006 - 7:54 PM EST
It's not the size of the screen. It's the resolution the screen is set for that's important. Most computers can be set for any of several at will. It used to be that 800 x 600 resolution was the most common in use. Now more people are using larger resolutions like 1024 x 768 and above.
Resolution means how many pixels across and down can display on the screen... but you also have to take a browser window interface into account as that takes up some screen room, too. How much room the browser takes up also varies by the browser. If you have a stats counter, screen resolution is usually returned as a stat so you can check what resolutions your own visitors are using.
Anyway, if this were me, I'd size for the smallest common denominator or screen resolution expected which in my own case would be 800x600. I'd size the largest pics no more than 780 pixels wide. That should accomodate most everybody without anyone needing to scroll left to right.