In the output, is the content correctly formatted on browsers other than Firefox?
Where is the content located? Hosted on a web site? Do you know what kind of web server? (Apache on Unix/Windows, IIS, etc.)
If you open the developer console with F12, inspect the topics, do you see any errors in the error tab? If you select an item in the topic, what does Firefox show as CSS being applied?
Kind regards,
Willam