Reload web page(s) and bypass the cache.

• Press and hold Shift and left-click the Reload button.
• Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• Press "Cmd + Shift + R" (MAC)

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

"Clear the Cache":

• Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now"

"Remove Cookies" from sites causing problems:

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

Are there any general.useragent.* or override prefs like general.*.override prefs bold (user set) on the about:config page?

What are the connection settings?

You can find the connection settings in Tools > Options > Advanced : Network : Connection

See "Firefox connection settings":

• https://support.mozilla.com/kb/Firefox+cannot+load+websites+but+other+programs+can

Ok, I tried all of the above suggestions. Nothing worked. The settings are "use system proxy settings". I dont see any general.useragent.* or override prefs like general.*.override prefs that are bold.

I really appreciate your helping me.

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

See Basic Troubleshooting: Make a new profile:

• https://support.mozilla.com/kb/Basic+Troubleshooting#w_8-make-a-new-profile

There may be extensions and plugins installed by default in a new profile, so check that in "Tools > Add-ons > Extensions & Plugins" in case there are still problems.

If that new profile works then you can transfer some files from the old profile to that new profile (be careful not to copy corrupted files)

See:

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