I have been having this problem at a customer that the site on my developing machine it looked good when the site was rendered, but then when I moved everything to the test server it didn’t look quite the same.
I had had the same problem when I moved the source from my laptop to the developing machine, but then the solution was not the same as the one I finally found. The solution wasn’t that obvious and Google had the solution… The problem was that in an Intranet Zone IE8 is set to use the compability mode, ie render the pages as IE7. It all came clear to me when I found this blog post of Raj Kaimal.
The organization I’m at the moment has a very rigid IT-support so the solution wasn’t to make them change the settings. I just did as it’s said in this article at MSDN, but I set the HTTP Custom Response Header “X-UA-Compatible” to “IE=100″, ie IE8.