Reply Removed -- jclarkw

Hello,

Here are some issues that have been found to be solutions :

• extensions (check every extension)
• Heavy webpage content ( if the site has lots of animations and stuff, open task manager and see if that tab is the reason)
• Hardware acceleration issues : Try disabling it in Settings > General > Performance.
• Outdated graphics drivers (update in device manager)
• Clear cache and cookies or refreshing Firefox (Note that cookies can sign you out of some websites.
• or Malware

If not, it is most likely because that the CPU is older, and can't handle as much. Especially for one of my computers, sometimes it takes up to 50% CPU load when streaming videos.

Dear dessertdish -- Thanks much for the suggestions! One note regarding your old-hardware point: Although the hardware is indeed old, I also run Chrome on it; and moving the offending Web sites to Chrome, although it relieves the CPU usage by Firefox, does not replace it with a comparable usage by Chrome. This and the fact that the problem seemed to have a suddent (recent) onset suggested to me that it was a Firefox issue.

The best (unsatisfying) solution so far has been to use Chrome for anything that causes Firefox to load down the computer. Cheers! -- jclarkw