function isEmail(elm) {
    if (elm.value.indexOf("@") == "-1" || elm.value.indexOf(".") == "-1" || elm.value == "")
    return true;
    else return false;
}

function checkData_contactus() {
  	if (document.form_contactus.name.value.length == 0) {
		alert("Please enter your Name. ");
		document.form_contactus.name.focus();
       return false;
	};
	
	if (isEmail(document.form_contactus.email) == true) {
       alert("Please enter a valid Email address.");
		document.form_contactus.email.focus();
       return false;
    };

	if (document.form_contactus.math.value != 5) {
       alert("Please answer, 2 + 3 = ? ");
		document.form_contactus.math.focus();
       return false; 
	};

	return true;
}

$(function(){
  $('#submit').attr('disabled', false);
});