I have a new install on WP 1.5 at sellbetteronline.com where I am testing WordPress for my several websites.
I've tried several themes, including default, which is currently in place (4-18-05). I have not modified the themes.
Using IE, everything looks great, but formatting is lost in Firefox and Netscape 4.7. Most graphics don't even show up in FF or Netscape.
(The Admin stuff also looks good in IE, not in FF.)
I am able to view other WordPress sites correctly in my browsers, including the WordPress.org site.
I installed to the root of the domain rather than a subdirectory directory. Could this be a factor?