Type about:preferences#advanced<Enter> in the address bar.

Under Advanced, Select Network.

[v56+] Type about:preferences#general<enter> in the address bar. Look for Network. +++++++++++++++++++++ Look for Configure How Firefox Connects and press the Settings button. If you are using a proxy, make sure those settings are correct. If there is no proxy, first try No Proxy. If there is a problem, then try System Proxy.

Some problems occur when your Internet security program was set to trust the previous version of Firefox, but no longer recognizes your updated version as trusted. Now how to fix the problem: To allow Firefox to connect to the Internet again;

• Make sure your Internet security software is up-to-date (i.e. you are running the latest version).
• Remove Firefox from your program's list of trusted or recognized programs. For detailed instructions, see

Configure firewalls so that Firefox can access the Internet {web link}

Nope, didn't work. Seems like hard reboot works best.

Was the problem fixed, or does it come back?

Start your Computer in safe mode with network support. Then start Firefox. Try Secure websites. Is the problem still there?

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode Starting Any Computer In Safe Mode; Free Online Encyclopedia

Holy crap, I just started having the same problem! The Home page opens fine but whenever I try to go to a real site that's not Firefox-related the little dot just dances for all eternity and nothing happens. And, no, Fred's idea doesn't work for me either. Literally the ONLY thing that works is refreshing the whole browser, which means hunting down and re-installing my addons every dang TIME. Even re-installing doesn't work and Quantum doesn't allow me to go back to older versions because it hates its users.

Get your bloody act together, Mozilla! We shouldn't have to deal with this crap! Other browsers don't go through this so what's your excuse?

The people who answer questions here, for the most part, are other Firefox users volunteering their time (like me), not Mozilla employees or Firefox developers.

If you want to leave feedback for Firefox developers, you can go to the Firefox Help menu and select Submit Feedback... or use this link. Your feedback gets collected by a team of people who read it and gather data about the most common issues.