This is an example of how you can center a div in a way it will always be centered regardless the screen resolution.

You make a wrapper div and inside that you nest another div with content. Just add a margin of equal pixel size left and right to each side of the wrapper DIV and you have a centered fluid DIV.

In this example i placed my menu inside the content div and snugged it up the edges using negative margins. Because of IE6 i also needed to position the navigation container relative. If not, the layout breaks apart in IE.

I also used a right float next to the menu but this triggers the IE6 peekaboo bug because it touches the div content. To avoid it i also had to set a position relative to it. More on the peekaboobug.