The world's most recent nuclear attack on 9 August 1945 immediately springs to mind, as does Richard Nixon's resignatoin on 9 August 1973. But 9 August 1991 may be almost as important:
On this day 25 years ago the world's first website went live to the public. The site, created by Sir Tim Berners-Lee, was a basic text page with hyperlinked words that connected to other pages.
Berners-Lee used the public launch to outline his plan for the service, which would come to dominate life in the twenty-first century.
"The WWW project merges the techniques of information retrieval and hypertext to make an easy but powerful global information system," said Berners-Lee on the world's first public website. "The project started with the philosophy that much academic information should be freely available to anyone."
Then, on 1 October 1994, during my first year of law school, Berners-Lee founded the World Wide Web Consortium, and here we are.