Header and Browser Compatibility issues in Tabula Rasa?

[thoitaxh]

Problem SOLVED! Hey, so I'm using Google Chrome most of the time, and my Thor themed layout works fine in that (except for a few issues that I'm pretty sure I can figure out myself) but when I use a different browser (i.e. Internet Explorer or Firefox; I haven't tried any others) the header doesn't sit where I want to sit. Which is mostly I guess because I used position: absolute but I'm not sure how else to get it centered above my posts.

This is how I want it to look in all browsers and how it looks when I use Chrome. This is how it looks on Firefox and this is how it looks on IE.

In both IE and FF, the header is too far left for what I want.

This is the code I used:
#header { font-size: 0px; position:absolute; top:120px; left:-90px; background:transparent url(http://i.imgur.com/DfuXc.png) no-repeat top center; height:300px; width:100%; }


Also, in IE the sidebar doesn't show up. Could that be because I used position: fixed?

I'd be glad for any help!