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

"Clear the Cache":

• Firefox > Preferences > Advanced > Network > Offline Storage (Cache): "Clear Now"

"Remove Cookies" from sites causing problems:

• Firefox > Preferences > Privacy > Cookies: "Show Cookies"

You can also check the network.http.* prefs on the about:config page and reset all bold user set network.http prefs to the default value via the right-click context menu -> Reset.

• http://kb.mozillazine.org/about:config

This is the standard Firefox fix that does not work. The problem is not the cache nor is it the cookies. The issue is a firefox issue only and G-Mail can be opened in other browsers such as IE. This is so frustrating and everyone is still complaining there is no decent fix after many complaints. I've re-installed mozilla - still doesn't fix it.

Try to set the network.http.spdy prefs to false on the about:config page.

• network.http.spdy.enabled
• network.http.spdy.enabled.v2
• network.http.spdy.enabled.v3

You can also try to disable IPv6.
See:

• http://kb.mozillazine.org/Error_loading_websites