MacKeeper, go away!

[comphernation]

Reading the Apple Discussions thread, it seems pretty clear it's a pop-under or similar, which Safari's pop-up blocker won't prevent. Posters there report that GlimmerBlocker works to prevent such things.

For what it's worth, I use Saft with Safari Version 4.1.3 (4533.19.4) under Tiger (OS X 10.4.11), and these things never bother me anymore. Saft's 'Ad Blocker' lets one add specific URLs to block, for example:

*/Ads/*
*/ad/*
*/ads/*
*adclick*
*promotion*
*sponsor*
*/adserver*
*doubleclick*
*pagead*
*kolmic.com*
*.intellitxt.com*
*ads.yimg.com/*
*suitesmart.com*
*.bc.yahoo.com*
*wixi.com*
*fastclick*
*.quantcast.com*
*chitika.com/*
*.chitika.com/
*.chitika.net/
*/oascentral*
*revsci.net*
*stansberryresearch.com*
*/addserver.*
*ad.doubleclick.net*
*viruslivescan.com*
*burstnet.com*
*ifastnet.com*

... and so on. One can set it use regex matches if one knows how. I often go to the snopes.com site and get no pop-unders. I went to the wowhead.com site mentioned in the thread and got none, either. Saft isn't free, but it's been worth it to me. Other apps, perhaps some free ones, may work as well.

Hope this helps.