Question

What kind of jquery validation rule would you use to specify that if a particular checkbox (say, for example, checkbox1) is checked, a particular textarea (say, for example, textbox1) must have a non-blank value?

Answer 1

The required rule can be used with a dependency expression, as outlined in the documentation:

$("#test").validate({
    rules: {
        txtarea: {
            required: "#check1:checked"
        }
    }
});

Example: http://jsfiddle.net/andrewwhitaker/y8qhv/