Web usability guru Jakob Neilsen recently published results of two studies on people's visual attention while looking at web sites.  The results reinforce the need to for web design and application design to adhere to convention.  Keep the important information above the fold and on to the left.  Both of these articles are worth your 5 to 10 minutes. 

Scrolling and Attention

Summary:
Web users spend 80% of their time looking at information above the page fold. Although users do scroll, they allocate only 20% of their attention below the fold.

Horizontal Attention Leans Left

Summary:
Web users spend 69% of their time viewing the left half of the page and 30% viewing the right half. A conventional layout is thus more likely to make sites profitable.