IE float bug

I’ve tried with no success to fix how my site (http://www.weirdncrazy.com/universe) looks in IE — my sidebar should be next to the content (which works in Firefox), yet in IE it’s moved below it. I have a width defined for the content, which is floated left, and the sidebar which has an equal left margin. Both the content and sidebar are held in a wrapper div. My CSS is:

#wrapper {
width: 700px;
margin: 0 auto;
overflow: hidden;
}
#content {
float: left;
width: 70%;
margin-top: 20px;
}
#sidebar {
margin-left: 75%;
width: 25%;
margin-top: 20px;
}

Any ideas to make it line up? Thanks in advance.