> This feature has been removed from the Web. Though some browsers may still support it, it is in the process of being dropped. Do not use it in old or new projects. Pages or Web apps using it may break at any time.
It also won't work because <center> controls text alignment and will have no effect on the alignment of a div (it will center its contents, though) (also this isn't entirely true, centering text will also center divs in IE6 and earlier).