Web sites have gotten wider over the years. Today, a fixed width of 950 pixels is recommended — this to accommodate a screen resolution of 1024 x 768 pixels, which has become fairly standard for most web users.
A fixed width of 950 pixels allows for some empty space on both sides of the web page, allowing for the appearance of scroll bars, when necessary.
If you look at the web sites from some major players like cnn.com and yahoo.com, you will see that a liquid layout (where the web site fills the entire screen right to left) is rarely used any more.
Also a width of 950 allows enough room for several navigation links horizontally across the top, as well as sidebars both left and right, if desired.
Before you make a decision on how wide you would like the pages of your web site to be, take some time to look at other major web site to see how they display — you may be surprised at what you see!