Normally this means that the computers CPU is being overworked.

When do you get this? How long before it goes away?

Thanks for getting back to me-am a complete novice. Don't even know what CPU means! Get the "not responding" every time i try to log into my E-Mail or search engine - lasts longer than I have time to give at my age!

CPU = Central Processing Unit Basically, the 'brains' of the computer.

So, you start the computer, no problem. You start Firefox, no problem. But when you try to access some websites, there is a problem.

Is the problem on just a few sites, or most of them?

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

Many thanks,FredMcD Have tried the suggestion and will see what happens. You may have saved my sanity! Happy 80 year old

Using FF 53.0.3 under Windows 7 and have had spells of the not responding message but now (over the last 6 hours) the display consistently cycles between not responding and normal but it is non responsive when the display is normal with the exception that occasionally a tab I tried to close long ago is closed or some tab I wanted to see a while back is displayed. As I write this using IE, task manager shows that firefox.exe is using 50% of CPU time and IE is performing well.

Hi robey

You can try these steps in case of issues with web pages:

You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files.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

Clear the cache and remove the cookies from websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences).

"Clear the cache":

• Options/Preferences -> Advanced -> Network -> Cached Web Content: "Clear Now"

"Remove the cookies" from websites that cause problems.

• Options/Preferences -> Privacy -> "Use custom settings for history" -> Cookies: "Show Cookies"

Start Firefox in Safe Mode 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/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

FF always gets boged down if it runs lonmg enough! Generaly when it is useing too mauch CPU time, I restart the OS and do updates. This is the first time it got too bad to use with little warning. "You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files." is something to try in the future but in this case I terminated FF useing task manager and restarted it. It gave the this is embarising message and included tabs I had very slowly clsoed over hours as things to restart. I unchecked them along with aol mail which FF is often unable to restart and FF restarted and does not use excess CPU time. It seems that FF slowly gets bogged down with use and just restarting it is the refreshment it needs.

This should be marked as solution chosen but I see no way to do it.

This post belongs to another user. A solution for their question has already been marked.