Hi, I think I have just caught the train of google shok horror thread of negative margin :)
I usually try to avoid the negative margin because never learn how to make it displays nicely in IE, but there is this job I am doing now, requires a negative margin - I can't think of other easy way to make it the way client wanted it, and I try to avoid the absolute positioning. Here is an example page what needs to be done and you can see the CSS in the html file http://lotusseedsdesign.com/temp/floatedbox.html the image below the wrap div is the screen shot from IE. Basically I have the margin-top: -30px in the div.signup. The example float page from W3C that Gunlaug Sortun posted, in the example 3, second example doesn't work in IE http://www.w3.org/Style/CSS/Test/float-margin