The 1901 Census is finally back online, albeit for a limited period, after its unexpectedly successful launch back in January.

The census is running on test site from 9am to 7pm Monday to Saturday so that it can monitor usage and "further optimise the settings to ensure a good user experience for the high levels of demand we expect when we launch the service", according to a statement on the website.

Within three hours of the census launch in January 1.2 million amateur historians had logged on to the site, bringing it crashing to a halt. The necessary repairs and improvements to get it back online have taken nearly eight months to complete.

"We were completely bowled over by the response to the site and have been adapting our servers and technology to cope with demand," said a spokesman at the Public Records Office, which runs the site.

The site will allow users to search over 32 million individual's details, images of the original census pages and innumerable addresses.

Users will be charged for certain transactions such as downloading images, printing information and running certain searches. These fees are indicated before the transaction is completed.

The only worry for the Public Records Office is that too many people will log on to the test phase and cause the service to fall over again — so hold your fire until the site is fully up and running again.