My website contains valid XHTML 1.0 Transitional and valid CSS. It looks great in IE7, but in Firefox and IE6, the center DIV sits about 20 pixels too low. Could someone please have a look at my div.css and tell me what I'm doing wrong.

I've set up my three-column layout such that my content is higher on the page than my navigation, using negative margins, and this may be causing me grief.

www.friendly-skies.com

Ken

using negative margins, and this may be causing me grief.

Yes it will

css crossbrowser is something misterious for me.. my template worked well but if i used it with php, it changed.. either side bar or content sometimes not inline.. need refresh once or twice to fix... now i always use 2 cols layout
content : margin-right:200
sidebar : width 200;float right
to make it.. i use .padding class for padding in both div

for three cols layout i use
menu : width:200;float:left

order in php page
<div id=menu></div>
<div id=sidebar></div
<div id=content></div

some time not inline.. need some fixes

Well I can tell its the DIV spacing, but something that is NOT friendly with firefox;
<iframe src="http://rcm-ca.amazon.ca/e/cm?t=fries...1=FFFFFF&f=ifr" style="width:120px;height:240px;" scrolling="no" marginwidth="0" marginheight="0" frameborder="0"></iframe>

Ok, this is your main problem:

The content in the center column has a font size, which is correct in Internet Explorer, and therefore the size of the DIV/TABLE for the center column has been increased.

In firefox, the content has a smaller font size, and therefore it uses less space. Your iframe and images in the left column therefore overlap the footer, as this column does not "push" the content down (increasing the table/div without a height attribute).

To show what I mean by "push", see my link (hover over a link in the menu and the page goes smaller - doesnt work on firefox it is a deveopment):
http://cjnet.info/pages/projects/index.html