The monthly web server survey from Netcraft for May 2004 ahs found over 50 Million web sites Netcraft: May 2004 Web Server Survey Finds 50 Million Sites.
"The first Netcraft survey in August 1995 found 18,957 hosts. Previous milestones in the survey were reached in April 1997 (1 million sites), February 2000 (10 million), September 2000 (20 million) and July 2001 (30 million)."