That normally means the computers CPU is being overworked.

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?

https://support.mozilla.org/en-US/kb/websites-look-wrong-or-appear-differently

https://support.mozilla.org/en-US/kb/firefox-slow-how-make-it-faster

https://support.mozilla.org/en-US/kb/firefox-uses-too-many-cpu-resources-how-fix

https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding

https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding

FredMcD, thank you for your reply. I tried running in safe mode, and while I didn't see the message "Firefox not responding" any longer at the top of the screen, actually my web browsing became worse running in safe mode? The various web sites I use became more troublesome? So, while in safe mode I don't see the message regarding Firefox, the actual browsing hasn't been any better. Any possible solutions, or opinions? Thank you.

It could be the work of one of your add-ons. Type about:addons<enter> in the address bar to open your Add-ons Manager. Hot key; <Control>(Mac=<Command>)<Shift> A)

In the Add-ons Manager, on the left, select Extensions. Disable a few add-ons, then Restart Firefox.

Some added toolbar and anti-virus add-ons are known to cause Firefox issues. Disable All of them.

If the problem continues, disable some more (restarting FF). Continue until the problem is gone. After, you know what group is causing the issue. Re-enable the last group ONE AT A TIME (restarting FF) until the problem returns.

Once you think you found the problem, disable that and re-enable all the others, then restart again. Let us know who the suspect is, detective.

FredMcD, thank you for your reply. When I enter the extensions window, I only see 2 items. The first being Adblock plus. The second being Firefox Hotfix. It shows that that item (F.F. Hotfix) is disabled. It also says that Firefox Hotfix is not compatible with Forefox 40.0.1. There is a box that states remove, along side of that option (F.F. Hotfix). Sort of confused though, if it says it is disabled, why is there a box to remove it? Should I click on the box to remove it anyway? Of the two options, I would probably try deleting F.F. Hotfix first, then the Adblock option. If I only see those two options in the extension list, and therefore those are the only two things I can remove, it will be one at a time, as you suggest. Just confused about the F.F. Hotfix issue, FredMcD. Thank you for your help.

Your System Details shows you are using Firefox 49.0

What are you using? https://support.mozilla.org/en-US/kb/update-firefox-latest-version

Hi FredMcD, when I check, I see it says I'm using version 49.0.1. I don't know if 49.0., as you state, is different than 49.0.1.? What do you suggest now? Once again, thank you for your help.

The reason I asked was because;

sciencemagic said

Firefox Hotfix is not compatible with Forefox 40.0.1

Perhaps that was a typo.

I'm calling for more help.

FredMcD, thank you for your reply. It was not a typo, FredMcD. The statement was 49.0.1. was not compatible, and evidently that is the version I have. Please let me know what you think after you get more help about the issue. Thank you, FredMcD.

Hi FredMcD, I haven't heard back from you after your comment of "I'm calling for more help" regarding my Firefox issue. Can you please give me your input FredMcD. Thank you.

I'll call again.

What does about:performance page says when this problem occurs?

Hi alex, thank you for your reply. Being this problem of slow operation with my browser is pretty much constant, not sure how "about performance" should be used. When I access the page, about performance, it seems to be a lot of mumbo jumbo I can't comprehend frankly. How are you suggesting I use the link, alex? If I access the link, "about performance" how do I make any changes to my browser, alex? Thank you, alex. Oh by the way, I am now evidently using Firefox version 49.0.2.. And, Firefox say's "Firefox Hotfix 20160826.01 is disabled" because it is not compatible with it?

http://www.ghacks.net/2015/08/03/mozilla-improves-aboutperformance-page-in-latest-firefox-nightly/ explains how to use about:performance page.

You might want to follow https://developer.mozilla.org/en-US/docs/Mozilla/Performance/Reporting_a_Performance_Problem as well.

Please let us know if this solves your question.

Hi alex, thank you for your reply. When I type in about:performance, I see a few things. It shows my adblocker may be slowing down my browser. It also said that about:performance also may be slowing down my browser. So, now I'm some what confused. The whole reason for the ad blocker was to hopefully eliminate that ads and thus possibly speed up my web browsing? Insofar as about:performance slowing up my browser, how can it be used then? If it is going to be a problem in the first place, how could or should I use it alex? I do like the idea of the service, in that it shows whats happening with ad-ons and evidently a given web site. But if it is creating a problem in it self, how can I use the feature? Thank you alex.

As a test, disable the ad blocker. Is the problem still there?

Hi FredMcD, I will try that. But, I'm sort of confused about how to use the feature "about:performance". I understand from the info I've seen how it is suppose to work. But, I really don't see it working for me that way. When I load a given site, and I want to see how about:performance is showing that web site performing, I can't see the results as it seems it should be presented, when using the feature about:performance. I.E., when at a given web site and I type in "about:performance" in the address bar, when in that site, I don't see the performance for that given site. And, I thought that was what it is all about in using that feature. Am I doing some thing wrong, or do I misunderstand the feature of about:performance? Can you please explain. Thank you.

I don't know about:performance

Hi alex_mayorga, can you please respond to my last response concerning about:performance. This is it. But, I'm sort of confused about how to use the feature "about:performance". I understand from the info I've seen how it is suppose to work. But, I really don't see it working for me that way. When I load a given site, and I want to see how about:performance is showing that web site performing, I can't see the results as it seems it should be presented, when using the feature about:performance. I.E., when at a given web site and I type in "about:performance" in the address bar, when in that site, I don't see the performance for that given site. And, I thought that was what it is all about in using that feature. Am I doing some thing wrong, or do I misunderstand the feature of about:performance? Can you please explain. Thank you.

about:performance

I am not too sure the about:performance page is always too helpful. I get the impression that the page will always try to report problems but when there are not really any problems it still shows what is having the most impact, and possibly that is a bit misleading if you do not actually have problems.

Some of those tools are very advanced and designed to help web developers troubleshoot issues of webpage design.

Please attach a screenshot of your about:performance page. It could highlight something important and we don't want to miss it now you have tried it.

• How do I create a screenshot of my problem?

Before we go any further lets go back to the original question. You see Firefox not responding

• Are you still seeing that ?
  • If so do you ever see that on this forum or only on other websites.
  • What sites do you routinely see that on, can you give an example that is public and does not need signing in.
• Are the problem sites ones with games, videos or large databases ?
• How many tabs do you normally have open on Firefox roughly 2-3,10,100,couple of hundred, thousands?

What's the issue ?

Have you tried to look at and carefully read the article Fred linked to

• Firefox hangs or is not responding - How to fix

Can you try to identify which of the situations that article mentions as being applicable to you ?

Open Threads

I also note you have current open questions

• This one -> poor browser performance lately /questions/1142608
• Why is it that internet speed from a provider has little effect on computer browser speed? /questions/1146033
• There are quite a few other problems you have asked about and I am not sure they were resolved satisfactorily search

Troubleshooting Information

Please post a copy of your full troubleshooting information page. Please put that in its own reply as it takes up a lot of room. Please also edit out the print related information as that will not have any bearing on this question

• See Use the Troubleshooting Information page to help fix Firefox issues

Refresh | New Profile

I suggest for now you do NOT attempt a Firefox refresh. That may help but it may be better for several reasons to try a slightly better and more advanced technique of creating an additional new profile. Lets wait for the troubleshooting information. Then see which method you would prefer to try

• Refresh Firefox - reset add-ons and settings
  • A simple mouse click method, but you will lose all extensions. It is complicated to try to effectively reverse it.
• Profile Manager - Create, remove or switch Firefox profiles
  • Not too difficult. Keeps extensions. A much better and more flexible option.

To find the correct solution to your problem, we need some more non-personal information from you. Please do the following:

1. Use ONE of these methods to open the Firefox Troubleshooting Information page:
   • Click the menu button , click on help and select Troubleshooting Information.
   • Type about:support into the Firefox address bar and press the enter key.
2. At the top of the Troubleshooting Information page that comes up, you should see a button that says "Copy text to clipboard". Click it.
3. Now, go back to your forum post, right-click in the reply box and select Paste from the context menu (or else click inside the reply box and press the Ctrl+V keys) to paste all the information you copied into the forum post.

If you need further information about the Troubleshooting information page, please read the article Use the Troubleshooting Information page to help fix Firefox issues.

Thanks in advance for your help!

Hi john99, thanks for your reply. It will take some time to fully respond to your detailed response and questions. I do appreciate your detailed response though. I'll just take a few questions at a time though, if that's OK.

Yes, I still do get the FF not responding on some sites. I do not see that message here, on this site. I usually see it when using Yahoo Finance, weatherunderground, the weather.com and some others. I usually have only one or two tabs open when navigating on the web.

The question about internet speed was not related to FF problems, just a valid question about my computer and browsing speed on FF. I have tried various fixes as per FF contributors, and still see the same problems. Just not sure if the problem is my computer or a browsing problem in general. I do experience the same problems with other browsers though, and that in it's self may be important to you? Being I'm not a computer expert, I do have some problems when I have to get very technical performing some suggestions that are asked. But, usually I muddle through. I do have some problems with trying to get screen shots, just don't do those kind of things very often.

I will not refresh FF as you suggest, and I sort of think I may tried that at some time in the past anyway, to no avail. I also believe I may have tried "about:support" at some time, just not sure after the amount of time that has gone by frankly. But, if I did, and being I'm seeing the same issue, it didn't solve the problem. But, frankly just not sure any longer john99. I will try your suggestions though nonetheless. Just please be patient with me, again, I'm not a computer wizard.

I will get back with you after I have some of your suggestions. In the mean while, you do have some info I have given you regarding some questions you asked. I do appreciate your help, thank you john99.