Hello Laura.

Are you talking about blocking access to the sites? If that's the cause, you can do it by using an extension that blocks unwanted sites (BlockSite for example) at your choice, or you can do it using third party software (like a Firewall, for example). There is both free and paid software of that kind. But Firefox doesn't include that feature by default, you'll need an extension for that.

Also, and a lthough possibly not related to your problem, I will remind you that the version of Firefox you are using at the moment as been discontinued and is no longer supported. Furthermore, it has known bugs and security problems. I urge you to update to the latest version of Firefox, for maximum stability, performance, security and usability. You can get it for free, as always, at getfirefox.com.

Best to use the HOSTS file, it will block websites for all users and browsers on that PC. http://en.wikipedia.org/wiki/HOSTS#Internet_resources_blocking

http://windowsdevcenter.com/lpt/a/4730 http://accs-net.com/hosts/