Click to suit your screen
Fixed and variable width CSS layouts both have their strengths and weaknesses, and have each been adopted widely, but there is a third way.
We can now set up multiple alternate style sheets, each with different styles applied, and the user change between them. My homepage is styled with a fixed width of 800px, but a user can click on the links at the top of the right column to change this width to suit their screen, be it a portable device, wide screen or standard.
This approach overcomes the two main issues associated with fixed width layouts, namely, that either they are too wide for your screen and necessitate horizontal scrolling, or, that they look lost in a sea of emptiness on your snazzy high-res screen. It also does not suffer the problem often criticized of variable width solutions; that they can produce paragraph widths too wide as to be comfortable to read. The widths can be chosen and tested before anyone applies them.
There is no reason, however, that one of these methods should not be available to the user, or even set as default. We could have a standard width for the page, for example, and a "match my screen size" button for those who felt the standard width was not appropriate for their screens. What I am proposing is that users should have the choice over how best to view content in their own browsers.