There are over 1 billion websites on the world wide web today. This milestone was first reached in September of 2014, as confirmed by NetCraft in its October 2014 Web Server Survey and first estimated and announced by Internet Live Stat (see the tweet from the inventor of the World Wide Web, Tim Berners-Lee). The number had subsequently declined, reverting back to a level below 1 billion (due to the monthly fluctuations in the count of inactive websites) before reaching again and stabilizing above the 1 billion mark starting in March of 2016. From 1 website in 1991 to 1 billion in 2014, the chart and table below show the total number of websites by year throughout history:
By "Website" we mean unique hostname (a name which can be resolved, using a name server, into an IP Address).
It must be noted that around 75% of websites today are not active, but parked domains or similar. 
|Websites||Change||Internet Users||Users per
|1995||23,500||758%||44,838,900||1,908||Altavista, Amazon, AuctionWeb|
|Aug. 1991||1||World Wide Web Project|
Source: NetCraft and Internet Live Stat (elaboration of data by Matthew Gray of MIT and Hobbes' Internet Timeline and Pingdom)
Periodic drops in the total count can depend on various factors, including an improvement in NetCraft's handling of wildcard hostnames. For example, in August 2012, over 40 million hostnames on only 242 IP addresses were removed from the Survey.
- The first-ever website (info.cern.ch) was published on August 6, 1991 by British physicist Tim Berners-Lee while at CERN, in Switzerland.  On April 30, 1993 CERN made World Wide Web ("W3" for short) technology available on a royalty-free basis to the public domain, allowing the Web to flourish.
- The World Wide Web was invented in March of 1989 by Tim Berners-Lee (see the original proposal). He also introduced the first web server, the first browser and editor (the “WorldWideWeb.app”), the Hypertext Transfer Protocol (HTTP) and, in October 1990, the first version of the "HyperText Markup Language" (HTML).
- In 2013 alone, the web has grown by more than one third: from about 630 million websites at the start of the year to over 850 million by December 2013 (of which 180 million were active).
- Over 50% of websites today are hosted on either Apache or nginx, both open source web servers. As of June 2014, Microsoft has got very close to Apache in terms of market share (only a 0.15% difference separates the two). If the trend continues, Microsoft could soon become the leading web server developer for the first time in history.
SourcesWorldometers' algorithm, which processes data elaborated through statistical analysis after being collected from the following sources:
- NetCraft Web Server Survey - [and its data compiled by Pingdom]. Netcraft Ltd.
- "Measuring the Growth of the Web." Matthew Gray, MIT.
- Robert H Zakon. "Hobbes' Internet Timeline - the definitive ARPAnet & Internet history." Zakon.org.
- "How we got from 1 to 162 million websites on the internet." Pingdom Tech blog. April 4, 2008.