restricting registration by age?

To start with, I'm a blind user and not a programmer at all!
I am setting up a website for pets and would like to make it age restricted - i.e. only people over the age of 13 can register and/or use the site.
I looked through the forums here and on Joomla but can't figure out how to make this happen. I did a google search and found some extensions that are no longer in business.
Can anyone help me with this, please??

thanks in advance,
Flip

oops, forgot, we're using Joomla 1.6.6 and CB 1.7 and plan on installing GroupJive with the YouGrids template from YouJoomla.

It all depends how severe you want the discrimination to be.

2 proposals:

1) a checkbox-type field (mandatory) at registration "I certify that I'm 13 years old or more"

2) a text-type field with server-side validation using a math exercise that a 13 years old can solve. E.g. "Proove your age through your capability: how much is 45 divided by 9 ?" and check for result.

What kind of checks did you have in mind ?

I was thinking of a simple date calculation. It's not earth-shattering to have it, but would be nice.
I want to say that an older version of CB had it, but I could be wrong. Also, I found a deprecated plugin called minage that no longer exists - the site that is.
I think maybe the checkbox idea would work - IF they are honest
Also, I guess putting the birthdate (full including year) to be mandatory on registration would help, could go back and double-check their age that way and ban those that lied on the checkbox.
But, I was hoping to be able to basically have them enter their birthdate in the field, there being an admin option for minimum age in the field and then it would automatically calculate if they're old enough would be ideal.
So, if anyone knows of a way to do that or perhaps a plugin that will do that, I'll keep checking back to see.
Thanks, Beat, for your suggestions, I'll see what I can come up with that will (hopefully) work for now. The math question, I don't think would work since I know too many adults that can't do math to save their butts - AND they could always use a calculator to get the answer since they ARE sitting at a computer and most computers have one built in.

Thanks again,
Flip

The best approach is to create a date field and ensure the minimum date can't be below your required age then set the field as required. Once done ensure in your Terms and Conditions (enabled from CB configuration) instructs users anyone below the age of XYZ is in violation. This protects you and your userbase. Unfortunately there is no way to FORCE age restrictions as anyone could just input whatever they want, but it removes your liability for them. This is the approach all other social sites have taken that I am aware of and seams reasonable.

thanks, Kyle.
is there any way to update the minage plugin so that it will work with CB 1.7? I was able to download an old copy of it, but I have no idea how to update it to work with the new and improved Joomla/CB. That's WAY above my abilities.
If I'm able to get it updated, I'll share it with the community for the same amount I paid for it - free!! That is, as long as the License allows that.

thanks again,
Flip

You're welcome to review the plugin or contact its developer regarding updating it. Please review other plugins for examples of CB API usage. You can also try sites like Joomlancers to hire a developer to upgrade it for you.