I have a div center-aligned that way:
<div id="container" style="position:absolute; top:0px; left:50%; margin-left:-500px; width:1000px;"></div>
As this solution Trying to center div horizontally and vertically in screen suggest.
The problem is that if the client's window's width (tried in FF 15.0.1) is smaller than 1000px the horizontal scrollbar won't allow to show the left side of the div.
Is there a pure html/css way to solve it?