Scores of well-known websites have been unavailable for large parts of Thursday because of problems with Amazon's web hosting service.
Foursquare, Reddit, Hootsuite and Quora were among the sites taken offline by the glitch.
Amazon EC2 is the retailer's cloud computing business. It provides processing power and storage to companies that do not have their own data centres.
No reason has so far been given for the outage.
Visitors to the website of location-based social network Foursquare were greeted by an apology.
"Our usually amazing datacentre hosts, Amazon EC2, are having a few hiccups this morning, which affected us and a bunch of other services that use them.
"Everything looks to be getting back to normal now," read the statement.
Quora website Information-sharing website Quora was also hit by the outage.
Amazon's cloud service last hit the headlines when it decided to stop hosting a mirrored version of the Wikileaks website.
Like a number of American-owned web hosts, it had come under pressure from the US government over the leaking of confidential State Department files.
Several of the web services that took action against Wikileaks suffered reprisal attacks by hackers.
However, at this stage, there is nothing to suggest that the most recent outage was related to the Wikileaks controversy.
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