Does it work if you use a normal http link?

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

"Clear the Cache":

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

"Remove Cookies" from sites causing problems:

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

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

thank first.the youtube problem is solve,but the checking your add-ons still pop up whenever i start firefox.i already clear the cache and cookies,try to start firefox in safe mode and check the default theme, but all these don't seem to solve my problems.and firefox always open up with two tabs along with 'welcome to firefox' ,how to disable it?

I also have same problem.

I tried to clear everything as cor-el wrote, but I still have this problem.

http://www.youtube.com- works fine https://www.youtube.com - shows what connection in Untrusted

Do you have any ideas what it could be?

Thanks a lot Jevgenij L.

Note that https://www.youtube.com/ has mixed content (i.e. some content comes via an unencrypted http connection).

You can see this in the "Web Developer > Web Console" (Ctrl+Shift+K) as lines marked in red text with [Mixed Content] added.

• https://developer.mozilla.org/en-US/docs/Security/MixedContent

Actually I can’t open any page what could be accessed thought HTTPS. I have attached warning message.

I tried to reinstall Browser.

You can check for problems with preferences and try to rename or delete the prefs.js file and possible numbered prefs-##.js files and a possible user.js file to reset all prefs to the default values.

• http://kb.mozillazine.org/Preferences_not_saved
• http://kb.mozillazine.org/Resetting_preferences

Create a new profile as a test to check if your current profile is causing the problems.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer some files from an existing profile to the new profile, but be careful not to copy corrupted files.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox