Make sure that you do not run Firefox in (permanent) Private Browsing mode (Never Remember History).

• https://support.mozilla.org/kb/Private+Browsing

In case you are using "Clear history when Firefox closes":

• do not clear the Site Preferences

• Tools > Options > Privacy > Firefox will: "Use custom settings for history": [X] "Clear history when Firefox closes" > Settings
• https://support.mozilla.org/kb/Clear+Recent+History

Note that clearing "Site Preferences" clears all exceptions for cookies, images, pop-up windows, software installation, and passwords and other site settings.

Thanks for your reply, cor-el. Unfortunately none of the two cases above applies to me. Firefox is set to remember all history and data, also I'm not using Private browsing.

To permanently disable:

1. In the address bar, type "about:config" and press Enter. 2. Click the "I'll be careful, I promise!" button. 3. In the search field, type "block_active". 4. Set the value for the one search result ("security.mixed_content.block_active_content") to "false".

In most cases that is not what the user needs. He/she should be able to disable this feature only on the selected websites. In my case, my intranet uses the filedepot plugin for the Drupal which was being blocked by the Firefox. It is annoying as we need to use it very often and to get it work, every time we need to click on the "Disable Protection on this page". However I'd need Firefox to block it on any other (especially 3rd party) websites. So as @maaxxify requests, a feature to disable this on certain website is more desirable.

Yes, this feature is terrible. If you insist on continuing down this path, you must put this feature in an area where normal humans can get to it, without having to type inscrutable messages. This completely breaks one of my asp.net sites and need to be able to tell regular people how to shut this maddening bug (yes, this is a bug not a feature) off. Where do I go to make suggestions like this? Thanks.

You may find a developers forum or mailing list where this could be considered on topic or has already been discussed

• http://www.mozilla.org/about/forums/#general-development

You should certainly make your thoughts known by posting a short comment here

• https://input.mozilla.org/en-US/feedback

Update

• see https://blog.mozilla.org/security/2013/05/16/mixed-content-blocking-in-firefox-aurora/
  • suggesting discussions in https://groups.google.com/forum/?fromgroups#!forum/mozilla.dev.security

To completely disable mixed content checking see screen snapshot here: http://plsqlnotes.blogspot.com/2013/09/firefox-disable-mixed-content-blocking.html

I agree the ability to disable MCB on a per-website basis is more desirable but since that solution doesn't currently exist, I posted the workaround to completely disable the feature.

By the way, some refinements are in the works. For example:

Bug #902156: Firefox 24 will remember your decision to suspend protection on a particular site if you continue browsing the site in the same tab. (Possibly also in new tabs, but I haven't checked.) However, if you navigate away from the site, when you go back, you'll have to click the shield again.

Bug #860712: Possible enhancement to extend the suspension of protection for a site for the duration of your Firefox session (might or might not continue after exiting Firefox and restoring your previous session). Still in discussion.

There are many other open bugs relating to this feature for those interested in researching...

Thanks jscher2000, this is helpful. Let's wait for Firefox 24 and hope the update will solve this tedious issue.

It's still a pain in the .... in version 26. I just want my decision to persist & not to have to keep telling it to unblock. But I also don't want to have to turn the feature off entirely. Pretty ridiculous situation.