I ask because I have been using firefox as the preferred browser since it first appeared some years ago.
Unfortunately all 4 of my computers were set to auto update and now 3 of them are unusable as firefox 'hangs' after the most recent update. The fourth was saved as I managed to turn off update before disaster happened.
I spent much time yesterday to put things right but so far have failed. All the advice on the firefox site is that downloading an earlier version is not the answer; why not?
If you aren't actively running anything else I would expect idle to be 99% and everything else to be 0% apart from Task Manager and your browser maybe occasionally rising to 1% (that's what I get with Chrome, even on a relatively old Pentium 4 single core 3GHz processor).