Negative Z-index on Firefox works! but…

Hayyy.. another CSS issue for Firefox. The negative z-index of Firefox puts the z-indexed div below the body, and I hate it. It should be like IE that ignores the body’s z-index. I don’t know what will I do to replace this z-index thing on firefox. It’s just because 20% of my top header needs a white background that’s why I’m using z-index so that the logo of my site will not be covered with the white background in fixed position. I thought it works fine in all browsers, but in Firefox, it doesn’t really work as I thought it was. I also assumed that FF doesn’t support Z-index properly. I tried to set my logo’s z-index to 2 and the background to 1, but it doesn’t display as expected… Huhuhu.. I hope someone can post a comment regarding this, or a link to a solved issue regarding this bug or maybe it’s not a bug, I just don’t know what’s the right terminology for it. Hehe ^_^ I have googled about this issue, but I didn’t find any answer.