KDE's startup notification for Firefox has been broken for a while,
it seems to work for the first use, but subsequently fails.
(the bouncing icon just keeps on bouncing until it times out)

So far, the "fix" for this has been to reduce the notification timeout
or to disable it altogether. Choices that are less than ideal.

Rumor has it that this will finally be working in Firefox 3.6,
but it is NOT yet fixed in the most recent beta (3.6b3).

I've never stopped looking for a solution to this annoyance,
and yesterday discovered a patch for Firefox (some discussion here and here)
that simply moves a chunk of code - and fixes the problem!

I had to rebuild Firefox with '--enable-startup-notification' to get this working.

In my opinion, the startup notification - whether it be the taskbar or the irritating bouncing icon - is one of those things that looks more usefull than it really is. Whether you use it or shut it off completely, you're left with the same info - my application did not start. In the case of the FF notification, you are actually left with impression that there is something wrong when in reality the problem is with the notification, not the application.

I choose to turn of all such notifications. If my app doesn't start, I will figure it pretty quickly and will then try to start it from a terminal to get some useful information as to what's going on and how I might fix it.

I use KDE and like it, but it tends to have some features that seem to serve no purpose except to look more sophisticated and important than they actually are. The obsession with tooltips that tell me what I can clearly allready see with my own 2 eyes is another I try to shut off - assuming I can even find out where each app controls this irritating feature.

If anyone's interested in recompiling Firefox and/or SeaMonkey
to get the startup notification feature working,
I uploaded patches and modified build scripts to github

They should work on Slackware 13.0 or later. 32 or 64 bit.
SeaMonkey 2.0.x may also build on Slackware 12.2,
I don't think the recent versions of Firefox will though.