Firefox plugin issue

[CourtesyFlush]

Sometimes when I go to websites and I will get a message at the top of the screen that a plugin was required to view content in it's entirety. Usually it's because there is sound on the page. I click on the button that says "Install missing plugins" and it shows me that I need a quicktime plugin. I will click next and it tells me that the quicktime plugin is not available and gives me a button for manual install. Basically this just installs Quicktime on my system, and does not give me the plugin in the browser. How do I fix this? Is there somewhere I can go to specifically get the quicktime plugin for firefox?
Thanks,

CF