UserContent.css in Chrome folder

Hello,
Could someone tell me how the usercontent file is used?
Is it just read from your profile.mozilla… folder.
I was trying to get the slow scrolling fixed and saw a post somewhere about adding this line:

/* Improve scroll performance on slow machines on some sites. */
{ background-attachment: scroll !important; }

to the file. I have done this and restarted FireFox, but with no noticeable difference. Are my text lines written correctly?

1 last thing…I do have 3d effects selected and I’m using the nvidia drivers from 1-click.

Thank you!

Hello…anyone out there!
I have since read that is seems like a bug in FF3.
Is there anyway to fix it, before an update comes?