This is what I'm using with my image right now:

img.sas{
position: absolute;
top:0;
left:100px;
margin:0;
z-index: -1;}

But this looks a little off with some resolutions.

Is there a way to position it relative to the CENTER of the page? So rather than 100px from the left side of the page, I want it to be XXpx to the left (or right?) from the CENTER of the page.