Type about:addons<enter> in the address bar to open the Add-ons Manager. Hot key; <Control>(Mac=<Command>) <Shift> A)

On the left side of the page, select Plugins. Make sure the ones you want to use are set to Ask or Allow.

Go to the web page. Once the page is loading, mouse to the address bar and Left click the icon. A window for displaying site information should come up. Select More Information. Now select Permissions. In the menu, Make sure the ones you want to use are set to Ask or Allow.

You can check that JavaScript is enabled and isn't blocked.

• javascript.enabled should be true on the about:config page

• http://kb.mozillazine.org/JavaScript
• https://support.mozilla.org/kb/JavaScript

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

If you use extensions (3-bar Menu button/Tools > Add-ons > Extensions) that can block content (e.g. Adblock Plus, NoScript, Flash Block, Ghostery) then make sure that such extensions do not block content. There is security software that can block content, so check that as well.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Create a new profile as a test to check if your current profile is causing the problem.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer files from a previously used profile to the new profile, but be cautious not to copy corrupted files to avoid carrying over problems.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Do lots of sites give you this error, or just a couple sites? If it's just a couple sites, you could post the addresses of those pages and indicate where you see the message (if there is a particular action you took before they showed up). That might point us toward the source of the problem if the above general troubleshooting steps do not help.

javascript is enabled in about:config, but it won't work on my Group Health website

mariellec2 said

javascript is enabled in about:config, but it won't work on my Group Health website

Hi mariellec2, since that sounds like a site involving personal information, you might want to check with the site provider on whether they know what is causing the problem, and use a different browser there for the time being.

I went to about:addons as FredMcD suggested but there is nothingabout javascript on the plugins page. I have no addons or extensions. And when he says "go to the web page" I don't know what web page he is referring to.

Hi mariellec2, changing how plugins are activated (automatically, upon your approval, or never) doesn't affect whether JavaScript runs, but some pages give a JavaScript error if a plugin they want to use is not enabled.

Since this presumably is a password-protected page, we can't look at it ourselves. However, you can check the address bar for a plugin notification icon, which looks like a small gray Lego block. If you see that, click it to see whether the page needs permission to run a plugin.