What program can I use to block nudity (porno sites) on Mozilla Firefox for FREE? I've researched some on the web, but the one's I've found are for IE. I really need this to protect my children... I've found that some sites have been viewed in my history. Please help!

Have a look through some of these extensions that filter your browser:
https://addons.mozilla.org/en-US/firefox/search?q=content+filter&status=4

Thanks Curlyben! I'll check those out! Merry Christmas!

Curlyben,
I just installed it! It's blocking the few websites I just tried to access. But, when I came back here to post this, it wouldn't allow me because "porno" was in the title of my question and "porno" keywords are blocked. So I had to go in and click to allow to see this. That could become annoying in the future. I'll just see how it goes. Thanks for the response.