Google mystery server runs 13% of active websites

The Google Web Server - custom-built server software used only by Google - now runs nearly 13 per cent of all active web sites, according to the latest survey data from the web-server-tracking UK research outfit Netcraft. Netcraft data has the Google Web Server (GWS) running nearly 11 million active sites - i.e., sites with recently updated content. This total includes not only sites run solely by Google, but also sites the company operates on behalf of third parties via services like Blogger, Google Docs, and Google App Engine. Apache is still the most prevalent web server, with nearly 44m active sites, and Microsoft servers are second with nearly 14m. But the Google Web Server tops all others and trails Microsoft by a mere 3m sites - despite being unavailable for use outside what Mountain View has called "the Google Network," a worldwide proprietary infrastructure that amounts to a private internet. Google does not discuss GWS. In the past, some reports have indicated that it's based on Apache. But in a 2007 web post, über Googler Matt Cutts indicated otherwise. "That's not correct," he wrote. "I believe GWS is a custom web server, not a modified version of Apache."

Source: http://www.theregister.co.uk/2010/01/29/google_web_server/