setting up mass subdomains and have immediate access to them

[kumsanto]

Does anyone know how for the scenarios of  blogspot or wordpress or
meetup subdomain URLs are generated immediately after user sign up. I
tried to follow methods mentioned in apache documentation
(http://httpd.apache.org/docs/1.3/vhosts/mass.html) and those things
work but it takes a while before those subdomains are visible from
remote computers.. i.e. after I set up user1.xxx.com and user2.xxx.com
, if user visits these URLs immediately there is no page available but
after some time these domains are available.. Any clues? Suggestions?