This tutorial provides the steps for making the internet safe on Mac OS X Lion for kids. You can enable safe browsing on Mac Lion by using the Parental Control Preferences.
Click the Apple icon and select Preferences from the menu list.
In the System Preferences window, Click the Parental Controls under System section
Unlock the Parental Control for editing then select the username (Kids Account) and navigate to Web tab
By selecting Allow access to only these websites, you can provide access to only the listed kids sites. If you want to customize the list of allowable and blocked sites then you can select the radio option with label as Try to limit access to adult websites automatically and then click the Customize button and enter the specific websites.