If you worry that your kids will go searching for porn online I think you should relax - porn will find your kid before any attempt to search for it there's no doubt about it - age has nothing to do with it! Obviously you can do something about this - pay for some expensive parental control software use some of the parental control capabilities that may be included with your antivirus or some all-in-one-system tool or... turn your Firefox into an environment that's safe and friendly for your kid(s) with Kid Mode - Firefox for Kids today's topic! ;)
Kid Mode - Firefox for Kids reached version 2.3 on the 6th of January 2011 but that doesn't mean it can be considered outdated in any way you can think of despite the fact it seems to have some minor issues here and there. With its official home available here this excellent Firefox addon comes with some numbers that don't lie as far as I can tell you: compatible with Firefox 3.5 - 4.0.* 372241 downloads so far and finally a rating of 4/5 stars after 22 user reviews.
To make a longer story short I must tell you that Kid Mode - Firefox for Kids sends your browser into full screen mode making access to other tabs (almost) impossible and providing your kids with a lot of things to do but... Alt+Tab works just as it happens with Ctrl+N; I think that paid Zoodles services aren't exactly great deals but I'd really like to see a lifetime membership becoming available. All in all there's a lot to discover here and to be honest this Firefox addon is the best one in its category that I've seen so far so... if you want to allow your kids to go online without your direct supervision Kid Mode - Firefox for Kids seems one of the best things around (just one more hint: it's available on virtually all platforms including Android as long as you can run Flash apps on your device). That's all folks! ;)