You can check the log in the Web Console for error messages and the Network Monitor (Firefox/Tools > Web Developer) to see how long it takes to load content. *https://developer.mozilla.org/Tools/Web_Console *https://developer.mozilla.org/Tools/Network_Monitor Use Ctrl+F5 or Ctrl+Shift+R to reload the page and bypass the cache to generate a fresh log. ---- Start Firefox in <u>[[Safe Mode|Safe Mode]]</u> to check if one of the extensions ("3-bar" menu button or Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem. *Switch to the DEFAULT theme: "3-bar" menu button or Tools > Add-ons > Appearance *Do NOT click the "Refresh Firefox" 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 to see if that has effect in case security software is causing problems. *http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/ *http://www.7tutorials.com/4-ways-boot-safe-mode-windows-10