Screen width?

[Meti]

I use the size 956 x 622 px

[redtom]

I design on 1000 X 1000px and code it with percentages instead of pixels, although sometimes you can't really use percent.

[Calon]

I open the document size as 1024px, but never use it all.

[QuickScriptz]

You'll find this helpful:
http://www.w3schools.com/browsers/browsers_display.asp

Google is your friend

[Jahova]

So, in other words, code it in % or;
1024x768 and higher.

[Tom-743]

http://tom743.awardspace.com/view.php for a list of screen sizes, they have all been done in the last few days. 1028 is the smallest so i wouldn't go over 1000px in a layout.

http://tom743.awardspace.com/screen.php to add your screen size