Millions of Google, Microsoft and Twitter users suffered service disruptions yesterday after all three firms reported technical difficulties.
Western European users of Microsoft's public cloud platform, Azure, were left without access for more than two hours at lunchtime yesterday.
"We apologise for any inconvenience this outage may have caused our customers," said the software giant in a status update on the Azure site.
"Customers who have questions regarding this incident are encouraged to contact customer service and support," it added.
Today's outage was the coincidental failure of two parallel systems at nearly the same time.
At the time of writing, Microsoft had released no further details about what caused the outage.
Users of online messaging service, Google Talk, were blighted by a service outage between 11am and 4pm UK time, which let them unable to send or receive messages.
In a series of service updates on the Google Apps Status blog, the search giant said the fault had affected "the majority" of users.
Members of social networking site Twitter were also unable to access the site for around 40 minutes yesterday, following a technical meltdown in two of its datacentres.
The firm's vice president of engineering, Mazen Rawahdeh, described the fault as an "infrastructural double whammy".
"Data centers are designed to be redundant: when one system fails (as everything does at one time or another), a parallel system takes over," he explained in a blog post.
"What was noteworthy about today's outage was the coincidental failure of two parallel systems at nearly the same time."
As reported by IT Pro yesterday, NatWest's online banking customers were locked out of its systems yesterday afternoon, although the firm's Twitter feed suggests the fault was fixed overnight.
