Firefox doesn't show PDFiles or open some pho

Hello,
My desktop Macintosh is all but useless. Anything that has to do with PDF only shows up as the pdf square with it's title. No visual.
Also most photographs, such as ones found in Hotmail or Craigslist only show the photographs title but not the image. I have to save certain files and open them in Preview. Often text blocks overlap each other obscuring themselves.
Is it my Mac, is it Foxfire? I've updated to the latest Foxfire.

My Mac is running 10.4.11

Thanks for the assistance.

JD