According to a quote from another newspaper, it was all down to someone having a slash in the wrong place!
As fear spread across the internet that hackers would bring the mighty search engine down and cause millions of pounds in damage, it emerged that the entire search engine was crashed by a rogue “/”.
Marissa Mayer, the vice-president of Google, explained the search engine has a list of harmful websites that it warns users not to visit. This afternoon a Google employee, whose job is to input the websites into the company’s system, accidentally typed “/” for the whole URL of a bad website. This caused Google to flag up every site with “/” in its URL as harmful, and blocked access.