Custom blocking page
Usually Parental Control Systems (PCS) show a standard blocking page when a minor requests a website not suitable for his age.
Using age.xml you can ask the PCS to redirect the minor user to an alternative URL rather than showing the blocking page. Not all PCS may install this functionality but it still makes sense to keep the users on your kids-friendly websites if you have any.
Important: Make sure that the target website / URL is open for minors. It should have an age.xml on it with age=0 or another low age rating. Otherwise your user may end up in a loop.
For redirection use the <alternate> tag that may be included in the <ageblock-labeltype>.
It is possible to redirect all blocked users to the same alternative website, or to redirect in an age-specific manner, e.g. kids to one page and teens to another.
Example of a redirection of all minors (requesting not suitabe content) to a kidsfriendly website:
Example of an age-specific redirection: