Problems with format and old browsers

I’m having problems with my WordPress blog when viewed in older web browsers. It views fine in my Firefox 3.5.9 and on another computer in IE8 but does not on my computer’s IE7 or another computer’s AOL web browser.

The unmodified theme I’m using is the MT-Dark theme which you can find here:

Here is how it’s supposed to look here.

And here is how it comes up incorrectly here.

Earlier the forums here helped me edit the stylesheet to modify the menus and remove the header text. I’m wondering if what I did may have violated some older brower standards or something. The edited header code is as follows:

#header {
    height: 340px;
	background:transparent url(img/header.jpg) no-repeat top ;
}
#header h1, #header h2{
	text-align:center;
	margin:10px auto 0;
    font-size:32px;
	line-height: 1em;
}
#header h1 a, #header h2 a{
    margin:0 0 350px 0;
	display:block;
	color:#B06604;
}
#header h1 a:hover, #header h2 a:hover{
	color:transparent;
}

Any help you can offer is much appreciated