PC Data has published its listing for the top 100 Web properties and sites for May 1999 and Yahoo! tops both categories. The Virginia-based company tracks the number of "unique visitors" who either go to a Web site or a Web property -- defined as a network of related sites. Every visitor is counted only once, regardless of how many times the individual visits a site. Here, The Register prints the top 10 in each category. May 1999 Top 10 Web Properties (a network of related sites) Web Property Unique Users (000) Yahoo 27,578 AOL Sites 26,599 Microsoft 23,801 Lycos 20,582 Go Network 14,956 NBC Internet 14,010 Excite Network 13,210 Time Warner Online 9,801 CNET 8,656 Real Networks 8,158 May 1999 Top 10 Web Sites Web site Unique users (000) yahoo.com 21,750 geocities.com 16,014 aol.com 15,018 netscape.com 14,791 msn.com 14,352 microsoft.com 12,183 lycos.com 11,383 excite.com 11,240 hotmail.com 10,784 tripod.com 10,448 ®