The current WordPress blog I'm editing is http://gomeffect.nl.orion.dnstemplate.com/ The official theme is WPRemix which I bought and edited later.
It looks great in IE but not in Firefox as it seems that Firefox does not use the css style sheet. If I use the original style sheet of the WPRemix theme, it works fine, but a minor change in the style sheet such as changing the Theme Name makes the website ugly in Firefox.
I found this question fairly specific and could not find similar problems in other topics. Thanks for any support!