function validateFields(){

		var illegalChars = /\W/; // allow only letters, underscores and numbers
		var filter  = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;

		if (document.f.first_name.value == ""){
			alert("Please enter your first name.");
			document.f.first_name.focus();
			return false;
		}
		if (document.f.last_name.value == ""){
			alert("Please enter your last name.");
			document.f.last_name.focus();
			return false;
		}
		
		if (document.f.email.value == ""){
			alert("Please enter your email address.");
			document.f.email.focus();
			return false;
		}
		if (!filter.test(document.f.email.value)){
			alert('Please enter a valid email address.');
			document.f.email.focus();
			return false;
		}
	}