Update your Java and check it out.. *https://www.mozilla.org/en-US/plugincheck/ *https://support.mozilla.org/en-US/kb/use-java-plugin-to-view-interactive-content

Try to disable hardware acceleration in Firefox. *Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available" *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes *https://hacks.mozilla.org/2010/09/hardware-acceleration/ Start Firefox in <u>[[Safe Mode|Safe Mode]]</u> 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