Here's something that may work for you. It's a little hacky, but if you're trying to find a good width for some text, this is the only way besides javascript that I know of. We're basically forcing the width by not allowing the line to break. You can put in <br/>
s if you need line breaks.
<div style="position:absolute;top:50px;left:50px;background:green;width:0px">
<div>
<div>test</div>
<div style="height:50px; white-space:nowrap">This is normally sized in IE6</div>
</div>
</div>
On second thought, don't check out the link. It's old and doesn't work as advertised.
Old answer:
http://snippets.dzone.com/posts/show/216
I believe that non-absolutely positioned DIVs automatically expand to fill their container horizontally. Since you haven't specified any container size for this div, it expands to fill the whole page.
I find it odd that Firefox doesn't expand the div... I'm not sure which of them actually has it "right".