To center a div on the screen,
align="center" is now deprecated by w3c,
if you want to center the div, use this instead:
<div style="margin-left:auto;margin-right:auto;width:900px"> ... </div>
and if you want to have fluid width, set it to % like:
<div style="margin-left:auto;margin-right:auto;width:90%"> ... </div>