//check that there's at least one character in the field and that the default value is not still in the field
 function isFilled(field) {
   if (field.value.length < 1 || field.value == field.defaultValue) {
     return false;
   } else {
     return true;
   }
 }

// check for presence of a "@" and a "." - if they're present it's good enough 
 function isEmail(field){
   if (field.value.indexOf("@") == -1 || field.value.indexOf(".") == -1){
     return false;
   } else {
     return true;
   }
 }

// check that required fields are filled and that email is valid 
 function validateForm(whichform,sumanswer){
   for (var i=0; i<whichform.elements.length; i++) {
     var element = whichform.elements[i];
	 if (element.className.indexOf("required") != -1) {
	 	//is required, so validate
		if (!isFilled(element)){
		  alert("Please fill in the "+element.name+" field.");
		  return false;
		}
	 }//end class required
	 if (element.className.indexOf("email") != -1){
	    // email is required, so validate
		if (!isEmail(element)){
			alert ("The " +element.name+ " field must be a valid email address.");
			return false;
		}
	 }//end email
	 //validate addition
	 if (element.className.indexOf("add") != -1){
	 	if(element.value != sumanswer){
			alert ("Please check your answer on the addition problem.");
	 		return false;
		}
	 }
   }//end for
   return true;
 } //end function
 
// generate random number
 function getRandom_0to10(){
    var seed = Math.random();
	return seed = Math.ceil(seed * 10); //Multiply to create number 0.0-9.99, then round to integer
 }
 var x = getRandom_0to10();
 var y = getRandom_0to10(); 
 var answer = x + y;