Gmail, Google's popular email service, crashed at approximately U.S. 11:45 AM ET/ 8:45 AM PT. At this time, we do not know why nor how this happened. Google has now said, "We experienced an issue with Gmail and some users experienced slow performance or errors. For everyone who was affected, we apologize - we know you count on Google to work for you, and we worked hard to restore normal operation for you. Although our engineering team is still fully engaged on investigation, we are confident we have established the root cause of the event and corrected it. Our current best estimate is that a significant subset of users' Gmail web queries were affected for an aggregate of 18 minutes, from ~08:54 - ~09:00 and then from ~09:04 - ~09:16 Pacific Time."
Other Google services, such as Google Docs, Google Talk, and iGoogle kept working. The Gmail site itself gave a 502 error code. This message typically means that there's a problem with the gateway or proxy servers between you and the core Web sites.
502 problems can also result from a Domain Name Server (DNS) problem. It seems likely to me that, since the Down for Everyone or Just for Me site reported that it couldn't even find the Gmail site on the Web.
Gmail came back up at about 12:15 PM ET / 9:15 AM PT and seems to be functioning normally. The trouble may not be over yet. A Google press representative said, "We are currently experiencing an issue with some Google services. For everyone who is affected, we apologize for any inconvenience you may be experiencing."