I've noticed more and more sites have gone to a fixed-width layout, where resizing the browser window just causes scrollbars to appear, as opposed to a flexible layout, where resizing the browser causes the components of the page to scrunch together.The StackExchange sites like this one are an example of the fixed layout.  GMail and iGoogle are examples of the flexible layout.  What are the reasons for choosing one over the other?
Fixed width vs dynamic width
website design
More complex designs can be very difficult to realize with variable width layout. So I imagine that plays a role.There is also the fact that it is not comfortable to read text that is very wide. The column size on StackExchange sites is quite manageable and easy to read. With a variable width layout, you can not just extend the main text body across without it becoming illegible. Even Google limits the width of their search results.Of course if you have a site where space is at a premium (like Google Docs and Google Maps) you really want to go with a variable width scheme to use all the available space. 