Amazon.com’s Alexa Internet Inc. subsidiary company is usually very reliable.  However, there was a temporary outage that caused some concern to many online publications.  Between May 20 and June 3, Alexa was not reporting updated traffic rankings on a daily basis.

Alexa is best known for their toolbar, an add-on to browsers that report a site’s 3 month ranking and harvests data for generating rankings.  On May 23, Alexa updated their toolbar for Firefox 3.0.

Amazon bought Alexa for $250 million in Amazon.com stock in 1999.  Alexa Internet is based in San Francisco, Calif.