The underlying ideas of the Web can be traced as far back as 1980, when Tim Berners-Lee and Robert Cailliau built ENQUIRE (short for Enquire Within Upon Everything, a book Berners-Lee recalled from his youth). While it was rather different from the Web we use today, it contained many of the same core ideas (and even some of the ideas of Berners-Lee's next project after the WWW, the Semantic Web).
In March 1989, Tim Berners-Lee wrote "Information Management: A Proposal", which referenced ENQUIRE and described a more elaborate information management system.  He published a more formal proposal for the actual World Wide Web on November 12, 1990 . Implementation began on November 13, 1990 when Berners-Lee wrote the first Web page  on a NeXT workstation.