Netcraft reports that the Web has grown by 1.24 million sites last month. They received responses from 63,523,742 hostnames, of which 26,877,351 were active.
Since the beginning of this year the Web has grown with an average of 1.2 million sites a month. Microsoft web servers had a slight share improvement of 0.25% in active sites that reversed several months of small gains by Apache.
About 70.29 percent of all active sites run on the Apache webserver. Microsoft, Sun and Zeus respectively have 22.2, 0.85 and 0.70 percent market share.
More info and detailed statistics of the May 2005 Web Server Survey at Netcraft