About:blank and Sp.html

I was infected with the above combination, which seems to be one of the variations of about:blank. After about 6 hours I cleaned it out. (my version seemd only to check if its files were there, I edited the contents of sp.html and deleted all files that had arrived on my machine at 13:27 on the day in question)
I then found a program which seemed to clean it from my other machine at http://www.rokop-security.de/main/article.php?sid=746
It is in german, but you can download ok, it deals with the sp.html variety.
My question for your experts is what is about:blank?
When I do an ASCII search of my hard drives I find lots of references to it especially in the AOL 9 folders.
On one forum a user actuall said that they wanted about:blank on their machine.
Views??
gradders