Inquisitive Minds launched its Zoodles safe-for-kids custom browser in May. Now it has launched an add-on for Firefox to let kids ages three to eight surf the web without the need for help or monitoring by parents.

The new Zoodles add-on converts the look and feel of Firefox so that even a kid who can’t read can understand how to browse through images of web sites and click on whatever they want to see, from videos to games. The simple interface is easy enough to navigate so kids can explore, play and learn on their own.

“We built Zoodles because we felt that the Internet experience was broken for young kids,” said Mark Williamson, chief executive and co-founder of Zoodles. “While there were many kids destinations out there, they were delivering a one-size-fits-all experience that was frustrating for both kids and parents.”

Zoodles tailors the browsing experience to the age of the child, giving the kids hundreds of options to choose from on the web. The web thus becomes a better babysitter than the TV. Zoodles screens and rates all of the content that kids can reach from the Zoodles browser or add-on. Parents can pay for a premium membership if they want more control over the child’s online experience. Since launching in May, the browser has more than 100,000 users.

In May, the company said it had raised $2.6 million in seed funding and had built the Zoodles Kids’ Browser on top of Adobe Air software. The product competes with Glubble and Kidzui, which have also created safe-browsing options for children.

Zoodles organizes its offering for kids in a different way. Upon signing up, it asks a parent to set the age level for the child playing. Zoodles then puts web sites that are geared toward that age on its menu. There are no URLs or other complex words for kids to decipher. There are just pictures of the apps. The kids click on them and they start playing. The approved sites are chosen by a team of education experts. The older a kid gets, the more the menu changes. Parents no longer have to constantly search for appropriate web sites.

Zoodles offers a free version but also has a premium subscription version. Williamson said the subscription fee of $55.95 a year is a lot cheaper than taking the kids out to see a movie. And Williamson said parents no longer have to look over the kids’ shoulder to see if they’re being safe. There is a 14-day free trial for full membership.

Williamson, a father of two, founded Inquisitive Minds in late 2008 after trying to get his oldest child to manage her own play time on PBSkids.org. But the child frequently clicked out of the web page and had to get help. Williamson wanted to find something, other than TV, that the child could do without any supervision. The company soft-launched the Zoodles beta in April 2009 and today is formally launching it. Tens of thousands of kids have logged more than 500,000 hours playing it so far.

Harrison Metal Capital led the round. The company has 6 full-time employees and is hiring.