An apparent system error left millions of visitors to the site puzzled when links to all search results were flagged with the warning 'This site may harm your computer'.
It is thought the site had erroneously identified all other websites - and some of its own pages - as containing malicious software or 'malware'.
The glitch, which prevented internet users from directly clicking through to search results, was fixed within 30 minutes although users of Google's email service Gmail have since reported finding genuine messages sent mistakenly to spam folders.
The errors prompted panic among web surfers who at first feared the popular search engine had suffered some kind of major failure that could have had serious implications for internet commerce.
The Google search page is by far the most popular on the internet, with the overall site receiving several hundred million queries each day. It is the most common homepage and accounts for almost four out of every five internet searches, making it a crucial part of the global economy.
Google automatically identifies sites that may carry viruses and harmful software as part of its searches, but on Saturday all sites that were searched for carried the warning.
It suggests that either every server on the internet had become infected with a virus, an unlikely scenario, or the Google security system had suffered a breakdown.
Users trying to access search results during the outage were forced to cut and past the links into the toolbar and visit the sites manually.
Surfers who tried to find out about the error were unable to access Google's own blog as it has also been incorrectly identified as a harmful link.
A Google spokesman said: "There was a fault. We don't know the nature of it yet. Everything has been solved. We are still making initial enquiries."
http://www.telegraph.co.uk/scienceandtechnology/technology/google/4413065/Millions-hit-by-Google-breakdown.html
