Recently I was by annoyed by a sound from a male that speaks “Congratulations, you won”, which kinda freaked me out when I am alone in midnight. The sound is automatically played every few minutes. Amazingly, I can even hear the sound when my Mac is idling in login screen.
So immediately I thought there is a popup ad but I can’t find any. At last, I found the culprit, it’s from a flash advertisement in YouTube. Can you imagine that? Here’s a screenshot of it, notice the pink box.
Anyway, I never trusted these kind of advertisement because I believe there’s no such thing as a free lunch in this world.
If you are using Mozilla Firefox and wanted to block the advertisements, you might want to check out Adblock Plus.

i already using this plugin and i think this uesful for everyone who want to browse the web without ads
Check out this thread for a solution:
http://www.google.ca/support/forum/p/youtube/thread?tid=2f01e50235d0b67a&hl=en&fid=2f01e50235d0b67a0004b9e8e9958530
In my case if was the Chrome SmoothScroll extension! Many people mention that this can’t be a legitimate Google ad, so it has to stem from a toll bar to extension you are running.
Thanks for the tips guys. I have used an adblocker before, but had bad poor results.
we just say ad is everywhere, but this is funny life flash to me, never notice such thing b4, thanks!
Yea..Its a cpa ad. The advertiser makes money when you click and sign up for a mailing list or something of that sort.