Hello,
The 'applications' tab in 'preferences' of Firefox 3.0.4 has only a few applications listed.
I am having problems with gif images and others not loading in the browser, although I can right click and open them one at a time manually.
I have tried disabling 'popup' blocking as well as disabling 'adblock'.
There are also some video playback problems.
I am guessing that if I can choose the application to run file types, then I can get the satisfactory behavior.
I am dual booting Slackware12.2 and Fedora10.
The apparently same version of Firefox in Fedora10 has a full list of applications to choose from in the 'applications' tab. This Slackware version seems not to.
M

Your problem has nothing to do with the applications listed in the applications tab... Those applications are only useful when firefox prompts you to "open with..." or "save as...".

I don't know what causes the problem with gif. It's very odd because firefox should be able to show gifs without dependencies. The video files usually require the installation of the flash plugin:

1) Go to adobe.com and download the flash plugin (get the .tar.gz package)
2) Untar the package by 'tar -xzf <package_file_name>'
3) Copy the file libflashplayer.so to /usr/lib/mozilla/plugins (the plugins directory may be different on Slackware)