How-To Geek

Fix "Security Error: Domain Name Mismatch" Warning in Firefox

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If you encounter this error message as often as I do, you will thank your various gods for this extension, which allows you to hide the warning message on a per site basis, for both Firefox as well as Thunderbird.

Here’s the default Firefox warning message… so irritating.

And here’s the same warning message once the extension is installed. This is the last time I saw this error for this particular bookmark. 

The extension will also allow you to hide the message for expired certificates as well. You can delete the remembered domains in the extension’s options panel.

Remember Mismatched Domains Extension – Mozilla Add-ons

Lowell Heddings, better known online as the How-To Geek, spends all his free time bringing you fresh geekery on a daily basis. You can follow him on if you'd like.

  • Published 05/8/07

Comments (9)

  1. Techie Buzz

    Cool tip, I have been seeing this error quite a lot of time while using the url for Google adsense where i typed instead of

    Now i will definitely be able to solve this errors i have been seeing.

  2. Jonathan

    Hey, thanks a lot for posting this bit of info. I recently tried switching all my IMAP accounts on thunderbird over to using SSL encryption. I then got inundated with this domain name mismatch errors every time I checked my mail for the first time after starting TB. I though there must be a way to hide these messages.
    I did a search on Google and a link to this blog entry was at the top of the list. Everything in the results looked unrelated. So yes, I am thanking my various Gods for both the extension and for your mentioning it here.

  3. Sridhar

    This is the problem that iam facing each time when i run application in firefox.
    but iam not getting this Security warning in IE.
    can u please give me a suggestion for this problem.
    Although this page is encrypted, the information you have entered is to be sent over an unencrypted connection and could easily be read by a third party
    Are you sure you want to continue sending this information?
    continue Cancel

    thanks in anticipation
    Sridhar Reddy

  4. Dick

    I had this problem with Firefox. I could not access my Yahoo email because of the error. I hired Ken to try to fix the problem. After about 45 minutes he found that the problem was with the new Firefox mail view. Switched back to Classic view for mail and the problem went away.

  5. What is Firefox?

    Note that this same extension works for Thunderbird as well. I’m using it there.

  6. Adrian

    I use Firefox on Ubuntu Gutsy but every time I close firefox, it asks me to check the box again. Every time. Anyone have a solution to this??

  7. naiem

    i have a problem with getting on firefox i dont know why if u place help me i iwll be reallly happy cuze i had this for 3 years maybe more then that if your really kind plz help me thx . :)

  8. Víctor


  9. laurentiu

    Your tip saved my nerves. My Firefox 2 is flooded with domain name miss match about which, by the way, I never visited.

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