This post was published back in 2008. It may not function as originally intended or may be missing images.
How To Disable 'will not be installed because it does not provide secure updates' Warning in Firefox 3
By default, Firefox 3 prevents users from installing any extensions that do not offer a secure connection for automatic updates. This prevents users from being victims of hijacked update URLs.
But for developers or people installing extensions they know they can trust, it is a pain.
Luckily it is easily disabled by:
- Enter 'about:config' into address bar, hit go
- Right click somewhere in the list of keys below. Select New->Boolean
- Enter ' extensions.checkUpdateSecurity ' as the name
- Select false as the value
- Reattempt installation of your plugin.
Found the solution at MozillaZine (via Google)