The HTML source of one of my web pages starts simplified with a code like:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<BODY BACKGROUND="images/myback.gif">
<div id="content" style="position: absolute; top: 0; left: 255px; width: 700px; z-index:-1; background-color: transparency;">
Blah blah blah

The page is displayed correctly in InternetExplorer but NOT in Firefox.
Is DIV really a pure IE extension?

How can I embed a similar code for Firefox as well ?