What is your computer system and Firefox?

Many site issues can be caused by corrupt cookies or cache.

• Clear the Cache and

• Remove Cookies
  Warning ! ! This will log you out of sites you're logged in to.

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

• Cookies; Select Privacy. Under History, select Firefox will Use Custom Settings. Press the button on the right side called Show Cookies. Use the search bar to look for the site. Note; There may be more than one entry. Remove All of them.
• Cache; Select Advanced > Network. Across from Cached Web Content, Press Clear Now.

If there is still a problem, Start Firefox in Safe Mode {web link} A small dialog should appear. Click Start In Safe Mode (not Refresh). While you are in safe mode;

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

Under Advanced, Select General. Look for and turn off Use Hardware Acceleration.

Poke around safe websites. Are there any problems?

Then restart.

You posted in the Firefox support fora queue. Firefox doesn't do email, it's strictly a web browser.

If you are using Firefox to access your mail, you are using "web-mail" such as Yahoo!Mail or Gmail. You need to seek support from your service provider or a forum for that service.

If your problem is with Thunderbird, let us know and we can move this thread to the Thunderbird support queue.

https://support.mozilla.org/en-US/kb/problems-with-email-how-to-find-help