DD Tab Menu I & II not view in Firefox

[caiser]

I have two pages I have designed using the DD Tab Menu II imaged based menu. However when I load them in firefox they tab images and background doesn't show up, but when I load it in Internet Explorer they do. Here are the links to the 2 pages.

http://u6.buildyourserver.com/rackmount%20chassis%20promotion.htm

http://u6.buildyourserver.com/system%20board%20promotion.htm

[caiser]

Dynamic Drive's tutorial page displays fine in Firefox, then why is my use of their Tab menu inoperable.

[caiser]

Anyone got any ideas?