Screen Resolution And Web Page Design

Read Optimal width for 1024px resolution?

I wish I did before I wrote all the following out...
The comments have both good information and a fixed vs fluid debate. Comment debates give me headaches.

Here's the archaic research I did:

Researching an old question for the newest answer.

1. Check Visitor Stats
2. If you have no stats history, Check Current Research - Preferably Industry and Geographically Specific

2001 [1]
Check your visitor stats
Reference online user surveys at WebSideStory and BrowserNews
They indicate that 800x600 is the most popular resolution, with 1024x768 close behind in 2001.
A page optimized for 800x600 should have a maximum width of about 760 pixels.

2005 [4]
The rightmost part of a page is cut off when printing a frozen page. This is especially true for Europeans, who use narrower paper (A4) than Americans
mistake #1 is to freeze the fonts - then they are too small for browsers

2006 [3]
Percentage Of Users:
1024 × 768 - 56% (2005) & 50% (2004)
800 × 600 - 28% (2005) & 35% (2004)

Screen Size In Browser:

For Screen size 800 × 600
IE 6 779 × 400
Firefox 781 × 434
Opera 777 × 427
Mozilla 779 × 420
Netscape 781 × 389

For Screen size 1024 × 768
IE 6 1003 × 568
Firefox 1005 × 602
Opera 1001 × 595
Mozilla 1003 × 588
Netscape 1005 × 557

"I use both fixed-width and percentage-based designs, and determine which to use based on user research, intended audience and client expectations. If I use a fixed-width design I tend towards an 800 × 600 screen size, usually around a 762 × 400 design size. If I use a percentage-based design I will design in stretch points so that the information looks good at both of the dominant screen sizes." - Joshua David McClurg-Genevese


Resources:
1. Screen Resolution And Page Design [Dec 2001]
2. Screen, which screen size should a web designer design for? [May 2000]
3. Designing for the Web [Jan 2006]
4. Top Ten Web Design Mistakes of 2005 [Oct 2005]

Read More:
Resolution Dependent Layout
Accessibilty Guide to Screen Resolution and Page Layout