"Our apologies to any of you who were inconvenienced this morning, and to site owners whose pages were incorrectly labelled," wrote Google Search VP Marissa Mayer yesterday, in a blogged explanation of the unfortunate fact than most Google searches conducted between 6:30AM-7:25AM PST on Saturday morning returned a message "This site may harm your computer" beside each and every search result. "This was clearly an error," Mayer added, "and we are very sorry for the inconvenience caused to our users."

Google works with a non-profit called StopBadware.org to come up with criteria for maintaining a list of sites known to install malicious software in the background or otherwise surreptitiously.

"We do this to protect our users against visiting sites that could harm their computers," explained Mayer, adding: "We maintain a list of such sites through both manual and automated methods."

Google periodically updates that list and released one such update to the site on Saturday morning, Mayer noted:

"Unfortunately (and here's the human error), the URL of '/' was mistakenly checked in as a value to the file and '/' expands to all URLs. Fortunately, our on-call site reliability team found the problem quickly and reverted the file. Since we push these updates in a staggered and rolling fashion, the errors began appearing between 6:27 a.m. and 6:40 a.m. and began disappearing between 7:10 and 7:25 a.m., so the duration of the problem for any particular user was approximately 40 minutes."

Mayer, whose full title is VP of Search Products & User Experience, promised that Google would carefully investigate this incident "and put more robust file checks in place to prevent it from happening again."

"Thanks for your understanding," her informative and candid explanatory blog post ended.