Internet users are finding that their access is slow and unreliable after destruction caused by terrorist attacks on Washington and New York paralyzed networks on Tuesday and continued to cause problems Wednesday.

Internet traffic surged in the moments after the first building collapse at the World Trade Center, as users flocked to news Web sites and sent frantic messages to loved ones. Internet performance monitoring firm Matrix.Net saw a spike in IP traffic shortly after the attacks, with the average "reachability" of Web sites dropping 8%, from 96% to 88%, beginning around 10 a.m. EDT.

News sites were particularly hard hit. According to a spokeswoman for New York Times Digital, NYTimes.com received an estimated 11.5 million page views Tuesday, exceeding their previous record of 9.6 million, set last year on the day after the presidential election.

With all that extra traffic, many users couldn't get to the news. To combat the problem, system administrators simplified site design to speed load times.

"Within the first hour, we removed most of the graphics, including the ads, from the entire site," the Times spokeswoman says. "We also removed the registration requirements, and that is still down."

Administrators at Times Digital were also able to reconfigure ad servers to help handle the extra traffic. "We have had heavy news days like this before," says the spokeswoman. "We just know to experiment."

At MSNBC.com, system administrators saw similarly high demand. "During the breaking news cycle, we had 10 times the amount of ordinary volume on the Web site," a spokesman says. "There were 300,000 to 400,000 users online at any given time." MSNBC also cut to "bare-bones-only news reporting" on its Web site, stripping graphics, video, and interactive content. The company added Web servers, even farming some of the job out to external vendors, including Akamai Technologies Inc.

Overall traffic levels quickly returned to nearly normal as system administrators dealt with the problem. "The really big dip in reachability lasted only about an hour," says John Quarterman, chief technology officer for Matrix.Net. "Some of the overloaded Web servers adapted their content to serve more users, and after awhile, users stopped trying so hard to reach overloaded servers and went elsewhere."

Wednesday was not expected to be an easier day for Web-site operators. The New York Times was expecting the day-after traffic to be higher than on the day of the disaster, as more Americans turn to sources other than television coverage.

Beyond the demands of surging traffic, Internet access has also been negatively affected by the physical damage to New York and the subsequent fires and power loss.

"There are lingering effects," Quarterman says. "In Manhattan, there are some nodes that just aren't there anymore or have no power."

With power out on much of the island, many servers are working on rapidly dwindling battery power. Machines are overheating as air conditioning shuts down or becomes clogged by debris. Several co-location centers in the World Trade Center are gone. And NYC.gov, the home page of the city government, is down.

But overall, most of the Internet infrastructure in Manhattan is still working, Quarterman says. "Automatic rerouting took place more or less immediately" when damage did occur, he says. "The Internet was designed to deal with problems where some of the infrastructure isn't there, and it worked well."