When Hemi Zucker's 8-year-old son began refusing to leave the computer for the dinner table, things came to a head.

His wife, frustrated by the many hours a week their son plays games online and his vehemence to stretch out the fun, banned the computer altogether.

"The computer is the 'c' word in our house," said Zucker, a Los Angeles resident.

The Zuckers aren't alone with the creeping feeling that their kids are spending too much time online. About a third of parents believe the Internet sucks up too much of their child's time, according to at least two studies this year. And an annual report from the University of Southern California's Annenberg School Center for the Digital Future shows that number has risen steadily since 2000, when only 11 percent of parents cited the issue.

To add perspective, nearly half of parents (48.6 percent) complained that their kids watch too much television in the 2007 study--the highest level in the six years of USC's digital future project. So TV certainly hasn't lost its stature in the home.

It's hard to predict whether the computer will outpace TV on the list of parental frustrations, but the studies and trends elevate its status. As more schools adopt a digital curriculum, children are spending more time in front of a computer screen at home and school to complete coursework. That alone could lend to a feeling among parents that kids are online too much. But where it gets sticky is that the Internet is also a hub for socializing, self-expression, play and time-shifted television, making it irresistible to more kids.

One parent described the phenomenon like this: "Their school life, TV life and their social networking is happening online," said Wayne Crews, a father of four in Fairfax, Wash. "Nobody knows how to bait a hook, but they know how to download and install a Windows file."

So how much is too much? Experts say there's no hard and fast rule for each family, and it should vary according to the child's age and school curriculum. Jim Steyer, founder and CEO of kids media-education group Common Sense Media, said pre-kindergarten children should likely stay off the computer altogether, but older "tweens" may need to spend an hour or more on the computer each day for homework.

"If it's getting in the way of other activities, like being outside and spending time with parents, then it's too much," Steyer said.

Steyer himself has a family rule that bars his kids from watching TV or playing computer games during the week because he and his wife want them to play outside.

How much time online?

On average, more than three-quarters of Americans age 12 and older spend about 8.9 hours online per week, up about an hour from a 2005 study from the USC-Annenberg Digital Future Project. But young people, specifically ages 8 to 18, spend about an hour on the computer and 49 minutes playing video games per day, according to the nonprofit Kaiser Family Foundation.

Crews, director of technology studies at the policy advocacy group Competitive Enterprise Institute, said his daughters, 8 and 11, are addicted to Webkinz, a virtual world populated by digital pets. But he and his wife limit the time they can spend playing and socializing on the site to about an hour a day (the same time limits they set with TV), so Crews takes a positive view of their time spent on the computer. That's particularly important considering the kids are doing more of their homework online and potentially watching streaming TV shows over broadband.

"The same way they might be watching TV and look down at a textbook, now they might be on Blackboard.com (a school curriculum Web site) and then toggle over to Webkinz," Crews said.

Crews' wife also limits their 13-year-old son to two hours a day playing computer games like Halo on the Xbox.

Crews added: "You don't want them to turn into jelly. You limit what they do, but I don't think they miss out on imaginative play by doing things online. They can get a lot more out of playing Halo than with the Play-Doh Fun Factory."

Some parents believe the computer is just supplanting the TV as the predominant screen in the home. But some industry experts say that the computer is different because it's more interactive--involving games and socializing. However, it's similar to TV in that it often means the child is sedentary. And some research has shown that computer games and the Internet can be more addictive than TV viewing.

Bobbie Carlton, director of marketing for Beacon Street Girls, a kids' social network, said she limits her boys, who are ages 5 and 10, to one hour of screen-time--whether it's video games, TV, DVDs or the computer--per day. And she enforces the time limit by setting a kitchen timer.

She added that it can be hard to always set a good example because she's online for work so much. "It's hard for the pot to be calling the kettle black," Carlton said.

Steyer said it's important for parents to set time limits for children when they're young, even if they're in preschool, so they know how much time they can spend online or with TV and video. He added that parents should keep the computer in a common family room, and talk regularly with their kids about what they do on the computer.

Still, the Zuckers aren't alone in taking the computer away. In 2006, USC reported that almost 50 percent of parents had withheld Internet use from their child as a form of punishment.

"Teaching kids that using the Web is a privilege not a right, that's very important from the beginning because good media habits can last a lifetime," Steyer said.