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Firefox (21.0) won't accept the security certificate for Twitter & won't let me add an exception.


My mother was having problems with her computer on the Internet and had to reset the modem. Problem was, I was on the Internet at the time using Twitter. She reset the modem, I thought everything was okay, but now Firefox isn't letting me access Twitter at all because of the security certificate. Here's the error message:

This Connection is Untrusted

         You have asked Firefox to connect

securely to twitter.com, but we can't confirm that your connection is secure.

         Normally, when you try to connect securely,

sites will present trusted identification to prove that you are going to the right place. However, this site's identity can't be verified.

         What Should I Do?
           If you usually connect to

this site without problems, this error could mean that someone is trying to impersonate the site, and you shouldn't continue.

twitter.com uses an invalid security certificate.

The certificate is not trusted because the issuer certificate is not trusted. The certificate is only valid for gateway.2wire.net

(Error code: sec_error_untrusted_issuer)

gatway.2wire.net is the default error page for my modem, if the Internet is not working at all. I think the problem here is that now Firefox thinks the legitimate site for Twitter is the error page and not, well, Twitter.com. Also, I'm not getting any "add exception" option. How do I fix this?

Additional System Details

Installed Plug-ins

  • Shockwave Flash 11.7 r700
  • Google Update
  • Next Generation Java Plug-in 10.17.2 for Mozilla browsers
  • NPRuntime Script Plug-in Library for Java(TM) Deploy
  • McAfee MSS+ NPAPI Plugin
  • VLC media player Web Plugin 2.0.2
  • Windows Presentation Foundation (WPF) plug-in for Mozilla browsers
  • DRM Netscape Network Object
  • Npdsplay dll
  • DRM Store Netscape Plugin


  • User Agent: Mozilla/5.0 (Windows NT 5.1; rv:21.0) Gecko/20100101 Firefox/21.0

More Information

  • Top 10 Contributor
  • Moderator
10783 solutions 97065 answers

Clear the cache and the cookies from websites that cause problems.

"Clear the Cache":

  • Firefox/Tools > Options > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

  • Firefox/Tools > Options > Privacy > Cookies: "Show Cookies"