CSS Rendering Problems

[instudios]

I'm in the process of designing my first CSS driven page with no tables, but I seem to be running into different rendering problems in different browsers. The page looks one way in Firefox and then looks another way in Internet Explorer, and I can't seem to pinpoint the problem. The url to the page is: http://www.netunification.com/demo/

I put together a page to better illustrate the rendering issues that I'm having, because it's somewhat hard to describe it using only words. The page has pictures to better explain. Please take a look at it. The url is: http://www.netunification.com/demo/reply.html

Please let me know if you have any suggestions

[emecks]

look at the "float:right" on your #DivMenu

also grab the webDeveloper toolbar for Firefox if you want to edit CSS more efficiently...

[instudios]

I removed the the "float:right" on my #DivMenu and it somewhat corrected the problem but not entirely. I haven't gotten a chance to view it in IE yet, but in Firefox (Mac) the design still has a slight gap above the menu tabs. . I have the #DivWrapper and Body margins set to zero so I can't understand why it's doing this. Take a look and tell me what you think.
http://www.netunification.com/demo/

I recently downloaded the web developers toolbar for Firefox and but I'm still in the process of learning all that it entails. Do you have any pointers?