Firefox is a powerful Web browser, in part, because of its support for plug-ins. Unfortunately, some of those plug-ins can cause problems with security and stability, especially if you have a lot of them. In Firefox 14, you can now configure plug-ins to load only when clicked. Seth Rosenblatt first reported on the feature with Firefox 14 Aurora. Now that the stable version of 14 (technically 14.01) is finally out, here's how to enable and use opt-in plug-ins in Firefox:
Enable opt-in plug-ins in Firefox
Step 1: In the address bar, type "about:config." When you get the warning prompt, click the "I'll be careful, I promise" button.
Step 2: Search for the "plugins.click_to_play" preference, then double-click on the entry so the value reads "true."
Opt-in/opt-out of plug-ins for individual sites
Step 1: After restarting your browser, go to one of your favorite Web sites. If your plug-ins are supported on that site, you'll see a plug-in block icon in the address bar.
Step 2: Click on the plug-in block icon, then click the "Activate plugins" button to allow them to run on the site during your visit. If you want to allow plug-ins to load on every subsequent visit, click the drop-down menu and choose "Always activate plugins for this site." If you want to permanently disable plug-ins on the site, select "Never activate plugins for this site" instead.
Manage your opt-in permissions
Step 1: To manage the permissions you've set for a site, click on the site-identity globe in the address bar, then click the "More Information" button.
Step 2: When the Page Info window appears, go to the permissions tab. You'll see the Activate Plugins permission at the very bottom.
That's it. Now you know how to set site-specific permissions for plug-ins in Firefox.