The death of Michael Jackson last Thursday triggered a spike in visits to news websites that adversely affected the performance and availability of some of the biggest sites. This included Google News, which interpreted the sharp spike in Jackson-related search queries as an automated attack.

Web monitoring company Keynote Systems found that between 6pm and 8pm Eastern Time (US), the availability for the news sites such as ABC, CBS and the LA Times dropped to almost 10 percent, meaning that about nine out of 10 visitors couldn't get the sites to load.

Starting at 5:30 pm, the average download speed for news sites tracked by Keynote went from less than four seconds to almost 9 seconds, and their average availability dropped from almost 100 percent to 86 percent, the company said. News sites monitored by Keynote returned to normal performance and availability levels by 9:15 pm.

Other news sites that experienced problems included AOL, MSNBC, NBC, the San Francisco Chronicle and Yahoo News, according to Keynote.

However, in a subsequent statement late Friday evening, Keynote noted that the slowdowns were caused primarily by external providers of interactive images and ads to the news sites. An example was the news site of ABC, which served up its internal content without delay but got dragged down by its external providers, Keynote said.

In these situations, depending on how a website is designed or how end users' browsers are configured, web pages can display immediately their internal content, leaving blank sections for the delayed external content or, at the other extreme, the pages will not be displayed until all components are ready to be rendered, according to Keynote.

"Ongoing end-to-end load testing and performance measurement benchmarking are essential to being prepared for unexpected news events. News sites should require third party content companies, such as ad networks, to certify the capacity of their networks, perform regular load tests from around the globe, and have strong Service Level Agreements in place," Keynote said in its statement Friday evening.

Meanwhile, Reuters' home page had a period of "significant slowdown" between around 6pm to 7pm, according to web monitoring company Pingdom.

Web monitoring company Gomez also noticed performance problems in the news sites it tracks, a spokeswoman said via email. At around 6pm on Thursday, the average response time in Gomez's online media web performance benchmark rose to 25 seconds, up from 11 seconds at the same time the day the previous day, she said.

Another high-profile news site that malfunctioned on Thursday was Google News, which interpreted the sharp spike in Jackson-related search queries as an automated attack. "As a result, for about 25 minutes Thursday, when some people searched Google News they saw a 'We're sorry' page before finding the articles they were looking for," Google said in an official blog on Friday. In general, Google saw a "volcanic" spike in Jackson-related search queries on Thursday, when more than 50 of the top-100 searches were related to him, a Google spokeswoman said via email.

Akamai's Net Usage Index for global news sites traffic surged at around 6pm and hit a peak of 4.24 million visitors per minute at 6:26 pm.

The usage spike also put a strain on online communication tools, like AOL's AIM instant messaging system, which went offline for about 40 minutes on Thursday.

Micro-blogging site Twitter disabled for several hours a search feature in its homepage, although the company didn't respond to a request for comment as to whether this was caused by a Jackson-related surge in usage.

Jackson died unexpectedly at the age of 50 from a heart attack in Los Angeles as he was reportedly getting ready to launch a comeback tour in London, England.