This site may harm your computer!

Google screwed up. Early Saturday morning the world’s biggest search engine marked every website on the Intertubes as a site that “may harm your computer!”
Within an hour or so, the problem was fixed. What happened?
Very simply, human error. Google flags search results with the message “This site may harm your computer” if the site is 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. We maintain a list of such sites through both manual and automated methods. We work with a non-profit called StopBadware.org to come up with criteria for maintaining this list, and to provide simple processes for webmasters to remove their site from the list.
That list included a website address listed as nothing more than “/” — so, every website in the world that had a slash in the address (read: every site in the world) was marked as one hosting a virus, trojan, or adware.
Source: Google Blog