What happens when a site as big — and essential — as Google.com is momentarily inaccessible? Traffic on the Internet falls off a cliff as people wait for it to come back online.On Friday, August 16, Google experienced a few minutes of downtime late in the day. It didn’t last long (5 minutes), but remember: this is a site that was recently estimated to account for 25% of all Internet traffic. For some third-party websites, the brief blackout sent traffic spiraling down by a whopping 40%.Analytics company GoSquared watched the dip happen in real time on Friday as it monitored more than 30,000 customer websites for traffic data. The trouble started at around 23:52, and it took just one minute for inbound pageviews to stall.It’s possible that GoSquared’s clients just happen to be websites that rely heavily upon incoming search traffic and have been built to attract it. When the world’s number one search engine is inaccessible — and therefore incapable of passing along visitors — search-optimized sites take a pounding.A 40% drop is enough to send chills down the spines of the people who pay the bills, but thankfully this was a very ephemeral drop. It was business as usual a few minutes later when the Google train was happily dropping off search passengers once again.Clearly web surfers were ecstatic when Google.com was responding once again. The massive spike that touched off at 23:57 was no doubt the result of people furiously re-submitting their queries and clicking through links to make up for lost time. Either that, or it’s from geeky types responding to innumerable panicked inquiries from friends and family about why Google wasn’t working.