Gmail was down on September 1st, 2009, for everyone.  How can we tell?  Google's Apps Status Dashboard:

Video:

Learn about the Google App Engine system status dashboard.

Screenshot:

Google Apps Status Dashboard offers "performance information" on Google Apps services.
URL: google.com/appsstatus

The screenshot above, taken on September 1st, 2009, shows that Google Mail's service was "disrupted" on that day and started on August 31st, 2009, the day before.  Use this for future reference when you cannot log into Gmail.

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External Links:

• Gmail
• Google Apps Status Dashboard

About the Author:  I am Matthew Doucette of Xona Games, an award-winning, indie game studio I run with my twin brother. We concentrate on nostalgic game concepts with modern-day gameplay and intensity. Our company, our games, and our technology have all won prestigious awards and received worldwide press. Our games have ranked from #1 in Canada to #1 in Japan, as well as become #1 best sellers in multiple countries. Read about our story and our blog.