function MM_validateForm() { //v4.0
  if (document.getElementById){
    var i,p,q,nm,test,num,min,max,errors='',args=MM_validateForm.arguments;
    for (i=0; i<(args.length-2); i+=3) { test=args[i+2]; val=document.getElementById(args[i]);
      if (val) { nm=val.name; if ((val=val.value)!="") {
        if (test.indexOf('isEmail')!=-1) { p=val.indexOf('@');
          if (p<1 || p==(val.length-1)) errors+='- '+nm+' must contain an e-mail address.\n';
        } else if (test!='R') { num = parseFloat(val);
          if (isNaN(val)) errors+='- '+nm+' must contain a number.\n';
          if (test.indexOf('inRange') != -1) { p=test.indexOf(':');
            min=test.substring(8,p); max=test.substring(p+1);
            if (num<min || max<num) errors+='- '+nm+' must contain a number between '+min+' and '+max+'.\n';
      } } } else if (test.charAt(0) == 'R') errors += '- '+nm+' is required.\n'; }
    } if (errors) alert('The following error(s) occurred:\n'+errors);
    document.MM_returnValue = (errors == '');
} }

$(document).ready(function(){  
	$("form#opt-in").submit(function() {  
  // we want to store the values from the form input box, then send via ajax below  
  var first_name    	 = $('#first_name').attr('value');  
  var last_name     	 = $('#last_name').attr('value');  
  var email_address		 = $('#email_address').attr('value');
  var campaign		 		 = $('#campaign').attr('value');
      $.ajax({  
          type: "POST",  
          url: 	"ajax.php",  
          data: "first_name="+ first_name +"& last_name="+ last_name +"& email_address="+ email_address +"& campaign=" + campaign,
          success: function(){  
              $('form#opt-in').hide(function(){$('div#opt-in-thanks').slideDown();});  
          }  
      });
  return false;
  });
});