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Performance and connectivity

Error codes

Troubleshoot issues with error codes.

In English

Secure connection failed and Firefox did not connect

Website will not allow Firefox to display the page if another site has embedded it

Fix "The bookmarks and history system will not be functional" error message

What do the security warning codes mean?

Warning Unresponsive script - What it means and how to fix it

Certificate contains the same serial number as another certificate

How to fix the Update Failed error message when updating Firefox

"Firefox is already running but is not responding" error - How to fix

Solutions for "Can not create temp folder archive" error when installing Firefox (Windows 10)

Websites say that Firefox is outdated or incompatible even though it's the latest version

Firefox says it's just updated every time it starts - how to fix

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