Comment 0 for bug 125970

User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.4a) Gecko/20030408 Phoenix/0.5+
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.4a) Gecko/20030408 Phoenix/0.5+

I discovered this is the site listed above. To verify this, I've visited several
sites in which a certain element can be set to have a position of either fixed
or relative--in all cases, so far, scrolling performance significantly decreases
when the element has a position of fixed. An easy example case follows:

Reproducible: Always

Steps to Reproduce:
10 Go to http://texturizer.net/phoenix/themes.html
20 Scroll -- speed is normal.
30 Move your mouse over the navigation menu.
40 "Lock Menu" should appear at the top of the menu. Click it.
50 Scroll -- speed is slow, very jerky.
60 Move your mouse over the navigation menu.
70 "Unlock Menu" should appear at the top of the menu. Click it.
80 GOTO 20: REM ^_^

This may be related to Bug 90198, but doesn't quite fit its direction. Bug 98252
also seems like it _could_ be related.

I'm not sure how well I've isolated this, but it seems that on pages including
fixed elements, scrolling is slowed considerably. Smooth-scroll, in particular,
can be very bad. Presently, I've focused on the CSS 'position: fixed' part of
this problem, but especially at the listed URL, there may be other nefarious
things at work.