More than a million people were disappointed when they tried to gain access to the Pubic Records Office website, where the 1901 Census was due to be published.
Within three hours 1.2 million had logged into the site to read the census, perhaps to gain a little information about who lived in their house 100 years ago.
The site, designed to cope with one million hits a day, was overrun with the demand and forced to shut down.
"We are very sorry for the chaos, but the demand was completely unexpected," said a spokeswoman at the PRO. "We are glad to see so many people are interested in local history and hope the site will be functioning fully soon."
It is the first time a census has been published online due to the standard 100-year moratorium.
Among the thousands of names listed are Charlie Chaplin and painter Claude Monet.
For more information visit www.pro.gov.uk.