I use Windows 7 with Firefox 54. When I accessed the link, the CPU does go up. But after a bit, it settles down.

I noticed what looks like several players on the page.

Yes, I suppose 54 does use some extra resources, on this page. However, all versions, up through 56, performed acceptably well, as you say. But at 57, this site, and others, bring the system to it's knees, within in a few minutes. Win10 may be a bit faster at this. 57 immediately jumps to 90% and the memory ramps right up, until the system stops responding - couple of minutes per Gb lost. I'm reasonably sure that all the reported 57 memory leak issues are due to certain web sites, and as you suggest, it may well be a media player problem. Not a single one of the suggested work-arounds will help weather.com and many other media enriched sites. I am positive this is repeatable!

One funny thing, though, is that the cpu goes to 90 and memory goes up, almost immediately, after the site begins to respond. It's like it starts to break FF, long before it attempts to load any media - almost like something in the page's header, is making FF cough, badly.

https://www.howtogeek.com/332449/whats-new-in-firefox-quantum/ Is called Quantum for a reason.

do this please : go to the Firefox 3 Bar Menu --> Options --> Privacy & Security panel and under Permissions check (put a tick in the box) the setting to Prevent Accessibility Services from accessing your browser.

Monitor in Task Manager. Should stay below 2 gigs. If excessive then do below and monitor and change if need to...Test and go up again , go back down, it will eventually get a zone you and it can live with.

Go to the 3 Bar Menu then Options --> General --> Performance and untick everything. change the recommended size lower then see how it runs. Note: 1 = No Multiprocessor = slow again. Try 2 Restart Firefox after making these changes please.

Please let us know if this solved your issue or if need further assistance.

W3C.org (World Wide Web Consortium) in charge of standards and practices and future development of both web page code and web browsers.

RESULTS for Weather.com HTML CHECKER - https://validator.w3.org/ HTML ERRORS - https://validator.w3.org/nu/?doc=https%3A%2F%2Fweather.com%2F CSS - CHECKER - https://jigsaw.w3.org/css-validator/ CSS ERRORS - https://jigsaw.w3.org/css-validator/validator?uri=Weather.com&profile=css3&usermedium=all&warning=1&vextwarning=&lang=en

So if this page their index was written/coded better there would be no issues at all with Firefox. The issues stem from trying to parse bad code.

Please let us know if this solved your issue or if need further assistance.

Thanks for the info. Just fyi: Edge and Chrome also leak, on this page. IE - no leak.

Accessibility Services was off. Setting Performance to 2 kept things well under 2Gb, but much still much higher memory and cpu than IE. However, setting to 1 even has IE beat, for total memory, on this nonconforming page.

So I'll tell my friends, and we don't need to give up FF, yet. After all, it's been a 12 year relationship, for me ;)

I suspect you might want to set the default performance a bit lower, though, for anything below an i7 - maybe even thene. 7 threads just won't fly, on a i5 or lower, and it seems I can only properly support 4 threads, on my old core2s.

Again, thank you. Solved...