stop flash ads in FF portable

Hey Folks
I got a tip to stop flash ads automatically playing by adding to the userChrome.css
but their is several directories named chrome in the portable install, I think I copied it into all of them, but it still seems to of had no effect..
which one is actually used?

the addition to the userChrome.css is:

/* Block Flash, using a placeholder you can click to unblock a desired Flash animation. */
/* Doesn't work for embed tags, which are less common than object tags - bug 190970 */
object[classid$=":D27CDB6E-AE6D-11cf-96B8-444553540000"],
object[codebase*="swflash.cab"] {
-moz-binding: url("http://www.cs.hmc.edu/~jruderma/flash.xml#obj"); }


any hints?
Ta