These availability charts from Keynote Systems show Amazon's U.K. site, top, dropping largely off the Net, then gradually recovering. The U.S. site, the lower chart, showed more intermittent problems.

(Credit: Keynote Systems)

Amazon.com's Web site was offline again Monday, another significant interruption of services after a two-hour outage Friday.

As of 10:08 PDT on Friday, Amazon's main Web site showed the "Http/1.1 Service Unavailable" error message that also showed on Friday.

The e-commerce giant's Friday outage affected its Amazon.com site used by U.S. visitors. Monday's outage appeared to affect its U.K. site as well.

Update 10:26 a.m. PDT: Amazon.com is back, though the U.K. site still appears down to me. On Friday, the site was intermittently available, though, so it does not appear to be out of the woods yet.

Update 10:40 a.m. PDT: The "We're sorry!" error page that showed up Friday also is appearing on some other pages. The site is working for me, but not for an East Coast colleague.

Update 10:47 a.m. PDT: Amazon.co.uk now works for me again, though with sporadic errors on product pages.

Update 10:59 a.m. PDT: The company still hasn't responded to my requests for comment, but Amazon acknowledged problems on a forum for those who sell goods at the site: "We are currently experiencing an issue that is causing site performance issues. Our engineers are actively engaged on resolving this issue, and we will continue to provide updates until service has been restored," the company said.

Update 11:07 a.m. PDT: I'm getting intermittent errors again at the main pages, and some product pages of Amazon.com and Amazon.co.uk. So it's clear that as with Friday, recovery is a fits-and-starts affair, even an hour after the problem began.

Update 11:58 a.m. PDT: Amazon.com and most of Amazon.co.uk are working for me. One curiosity: when the site was really struggling, it was rare to even get the "Sorry!" error page.

Outages are bad, but as eBay learned nearly a decade ago, multiple outages are worse. Over its history so far, though, Amazon generally has a reputation for reliability.

Update 12:28 p.m. PDT: Amazon has posted an "issue resolved" update to its seller community forum on Monday--but it's not about Monday's problem. Instead, it's just got old news, saying that on Friday, Amazon resolved the problem it was having on Friday. Still no word from the company about the second glitch.

Update 1:20 p.m. PDT: Keynote Systems, which monitors the availability of Web sites browsed from PCs and mobile devices, confirmed that Monday's outage hit the U.S. and U.K. sites.

The U.S. outage was a double whammy, said Shawn White, Keynote's director of external operations. The first problem showed from 10:03 a.m. to 10:23 a.m. PDT, with site availability dropping to about 30 percent. A second, less severe problem occurred from 10:56 a.m. to 11:09 a.m. PDT, he said.

The U.K. glitch was a single, longer-lasting outage that began at 10:06 a.m. and dropped the site to about 30 percent availability. The site gradually recovered over a period of about two hours to 50 percent, 70 percent, and now 98 percent.

"It stills look like some type of user error or configuration glitch," he said. "The data just doesn't demonstrate any kind of network-level attack."

Update 1:40 p.m. PDT: Amazon confirmed the problem, though it didn't share much detail: "Some customers reported intermittent problems accessing Amazon retail Web sites on Monday morning. However, we are working to resolve the issues, and Amazon's Web services are not affected."

Update 2:50 p.m. PDT: A reader and I just got more timeouts on the U.S. site, with not even an error message showing. Things still aren't totally up to snuff, apparently.

Also, I added some nicer graphs from Keynote.

Source: C.net