[iBook] Alt-Ctl-Del for Macs?

[gooddog at interlync.com]

Folks;

At work I use a Windows machine, and am used to using Task Manager via 
Alt-Ctl-Del to close/kill pop-up windows and various assorted things 
that crop up.  I can't figure out a way to deal with the new pop-under 
ads that I've been having on my iBook. Is there an equivalent of Task 
Manager on the Mac?  The "block pop-up ads" preference in Safari 
doesn't work on these pop-under ads.

Any suggestions?

Thanks.

Mark