[Javascript] Looking for simple validation script

[Pete Holsberg]

I need a simple script that will check two input boxes when
"submit" is clicked on.

One input is at least 4 letters and/or digits.

The other is at least 6 characters, that must include
letters and at least one digit.

Suitable "error" messages should appear that explain what
was wrong and bring the person back to the form.

Is there any thing simiar posted somewhere?

Thanks,
Pete