Firefox, preventing downloads

Hi there tech friends.
I am running Mozilla Firefox latest version on a iMac. My question is are there any ways of preventing the downloading of files on a user account? The Internet Explorer had this feature, but I cant seem to find in within Firefox. I want to set this iMac so that the downloading of files if not possible.
Thanks for your help.

I use Firefox on a PC. But I am wondering just what kind of files you're referring to.. To the best of my knowledge, the user has to accept a download-it doesn't just 'happen'.

Are you trying to limit downloads for a specific user? Restrict some access?

The only difference between a download to the HD and viewing a website page
is the file extension on the URL being accessed and the browser settings for
Opening it vs Saving it.

IE does 'interesting things' because it breaks the W3C standards and MS likes
to write their own rules.

Blocking access to some site is easy(by blocking the url),
also some types of content,
eg: blocking all *.zip, *.rar, *.exe