“It is impossible to be absolutely certain how many websites there are in the world but UK research company Netcraft have released their latest November survey of web servers and concluded there are about 525 million websites in the world today – a rise of 22 million (4.3%) since last month.
Interestingly, the number of active sites is only 172 million – so there are 353 million inactive sites.”
The January report from Netcraft states:
In the February 2012 survey we received responses from 612,843,429 sites. Compared to January, this represents an increase of 30M hostnames or +5.2%.