This was mentioned in bug 410330, comment 8: " Saw the same type of thing, extremely high CPU usage, on the following site: www.wcax.com (news site-lot's of flash, slideshows but those are not the problem) I confirmed that the scrolling info near the top of the page (yellow text in a thin read bar) was causing the problem, CPU @98%+. Hover over the scrolling the text (links in this case) stops the scrollin and CPU usage returns to 0%. I then found several other sites with similar scrolling text and saw the same amount of CPU usage. Other sites without scrolling text but with flash type ads (not all of them though), sometimes triggered the same type of usage. " I'm also seeing this. CPU usage on branch is appr. 10% for me. On trunk, I get CPU usage of appr. 50%. When hovering over the marquee, the CPU usage seems to be reduced to 20%. So I guess there might be some layout reflow code that is triggered while running the marquee or something. I suspect this is more or less the same issue as bug 383351.

Also this site does the same when they use the 'red/yellow' scrolling text. Seems that many TV station web-pages use the same format/template to create pages, and many are similiar and use the same technique. Therefore, I don't think its just a 'one-off' for a site doing something wrong with coding. Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9b4pre) Gecko/2008030305 Minefield/3.0b4pre Firefox/3.0 ID:2008030305 <- Latest nightly / Vista HP

I've had several of my cohorts bounce the nightly trunk builds against Firefox 2.0.0.x when viewing this site (WCAX-during storm alerts when the scroll bar is run) over the past couple of weeks and they've also reported the same thing. High CPU usage, between 70%-99% for trunk, 0%-20% for Firefox branch and IE 7.0/6.0 (peaks to 20% caused by "rolling" flash and sideshows etc). I've saved a local copy of the main page/images including the scroll bar. If anyone feels that might be of use please let me know and I'll attach it.

This bug related to: https://bugzilla.mozilla.org/show_bug.cgi?id=142994

This was a regression somewhere between Firefox 2 and Firefox 3, bug 142994 is a much older problem. Now, to confirm this bug, it needs a minimal testcase.

Checked provided url, no exceed CPU usage detected, it stays near 3-5% even while scrolling. Do you still see the problem on your side?