I need to say... if selectedIndex == 'Registered Users' or if the user selects the second option, add a class.

Code JavaScript:
if (privacy_form)
	{
		var dob = document.getElementById('dob'); 
 
		if (dob.options[1])
		{
			addClass(dob, 'db');
		}
		else
		{
			removeClass(dob, 'db');
		}
	}