Do you have the problem with any other website? Do you have the problem with any other web browser?

Go to the Control Panel and uninstall Mozilla, then download Mozilla from a trusted site and install. If your Windows 32-bit, Mozilla also has to be 32 bits. If you use Windows 8, Look for Mozilla for windows 8. Really helped for me and I have no problems now.

You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.

• Hold down the Shift key and left-click the Reload button
• Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• Press "Command + Shift + R" (Mac)

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.

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

Boot the computer in Windows Safe Mode with network support (press F8 on the boot screen) as a test to see if this helps.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/