Question about Margins

I wanted to have a margin in my footer area to make room for an image so i put in my css

margin: 150px auto;

You can see it below

#footer {
	clear: both;
	height: 50px;
	background: url(images/footer.png) no-repeat;
	position: relative;
        margin: 150px auto;

I checked in firefox and its perfect

I check in internet explorer ( hate that thing ) and instead of putting in the margin its just extended my content area

Like what the heck? Here is my site so you can see what i mean, look in firefox then in ie. any help appreciated thanks

http://tinyurl.com/yfov9au

By the way i have 3 stylesheets style.css ( this is where i put the code ) and i.e6.css and ie7.css ( i never placed anything in them