According to a Netcraft survey in September 2008 there were 181,277,835 active websites on the Internet.
When I checked the Netcraft site in September 2020 remarkably the site preserved documentation of the web back to March 11, 2002, making it probably a unique source of historical statistics on the web for the years between 2002 and 2020. I have attached an image of that report as it appeared on their site in September 2020.