I ought to have added that I have a single core CPU. It might not appear with dual core or higher as a problem.

I'm not sure what is going on with that blog. It regularly spiked up to 25-33% of a quad-core processor on this PC. I didn't even notice any video.

More generally, several users reported problems with slow rendering in Firefox 27. This long thread has more discussion on what people have tried to address that: Firefox is unbearably slow after updating to version 27. On older XP systems, one approach was to remove "cairo" as a back-end for Azure. Yes, that is gibberish out of context, but you can check it out. There is some danger that this "fix" will cause Firefox 28 to crash so you might wait and see how it turns out for people who try it.

I successfully applied the fix suggested in Firefox is unbearably slow after updating to version 27. This fix was also good for version 27.0.1.

However, upgraded to version 28 last night (with the same Firefox config settings) and Firefox CPU usage hit 99% and stayed there. The browser was totally unusable.

Therefore, went back to version 27.0.1 (I had kept a backup of the files), and Firefox was fast again.

Some of you running into and investigating this sort of problem may well be considering methods rather too complicated for run of the mill users and may wish to consider running multiple installs of Firefox and separate Firefox profiles.

If anyone does consider that then the following links may be of assistance

• http://kb.mozillazine.org/Testing_pre-release_versions#Installing_multiple_versions
• Profile Manager - Create, remove or switch Firefox profiles_creating-a-profile

Further suggestions could be made if anyone is considering directly comparing different Firefox versions and installs in this manner.

Having the same problem on a Win 7, dual core laptop. The only thing that has seemed to stop the problem was changing the Shockwave Flash plugin (12.0.0.77) to "ask to activate." It ran much better and stopped hogging resources after that. As soon as I activated it on a page, even after i closed that page, it continued to run, hanging Firefox again. I've had Firefox crash at least two time a day since i upgraded to 28.

Hi alisadm, one potential workaround for problems with Flash on Windows 7 is to disable the protected mode feature. The following pages provide different ways to disable that feature:

• Adobe support article under the heading "Last Resort": Adobe Forums: How do I troubleshoot Flash Player's protected mode for Firefox?

• Manual steps: https://support.mozilla.org/questions/968190?page=5#answer-509209

• Batch file to automate the manual steps: https://support.mozilla.org/questions/982093#answer-518078

Flash needs to completely unload from memory (restarting Firefox might help) before this would take effect.

Everything is jerky and sower with this new version of firefox - typing, scrolling, everything. It happens on single or multicore processors (firefox maxes out one processor every few seconds). It happens on XP32 and W7.

It is very difficult to type this message when the characters are only echoed in bunches every few seconds. I have tried many of the suggestions for work arounds and repairing firefox itself, without success.

Two questions: Is there a better option than to roll back to v26? Why aren't new versions of Firefox tested adequately by Mozilla?

Hi purchasemail, I guess there aren't enough testers to match all the possible system configurations.

Was Firefox 27 working well for you, or working well with the fix described earlier in this thread (removing cairo from a setting)?