var formError;


function validateForm(form) 
{
    formError = '';
    
	for (i=0; i<form.elements.length; i++) {
        if ("undefined" != typeof(form.elements[i].name)) {
             // required field
    	     if (form.elements[i].name.indexOf('string_') == 0) {
    	         formError += checkNotEmpty(form.elements[i]);
    	     // email address
    	     } else if (form.elements[i].name.indexOf('email_') == 0) {
        	     formError += checkEmail(form.elements[i]);
        	 }
	    }
	}

	if (formError != '') {
		alert(formError);
		return false;
	}
	
	return true;
}


function checkNotEmpty(field) 
{
	if (field.value == '') {
		if (formError == '') {
		    field.focus();
		}
		return "Please fill out your " + field.name.replace("string_", "") + ".\n";
	} else {
		return '';
	}
}


function checkEmail(field) 
{
	var filter=/^.+@.+\..{2,4}$/;
	if (!(filter.test(field.value))) {
		if (formError == '') {
		    field.focus();
		}
		return "Please enter a valid email address.\n";
	} else {
		return '';
	}
}