var mail = /^[0-9A-Za-z_\.\-]+@[0-9A-Za-z_\.\-]+\.[A-Za-z]{2,3}$/;

function check_form(form) {
	var msg = "Los campos indicados con (*) son obligatorios";

	for (var i=0; i < form.elements.length; i++) {
		if (form.elements[i].name.substr(0,2) == "r_") {
		   switch(form.elements[i].type) {
			case "text":
			case "password":
				if (form.elements[i].value.length == 0) {
					alert(msg);
					form.elements[i].focus();
					return false;
				}
				break;

			case "radio":
				var checked = 0;
				var radio = eval('document.' + form.name + '.' + form.elements[i].name);
				
				for (var j=0; j < radio.length; j++) {
					if (radio[j].checked == true) {
						checked = 1;
						break;
					}
				}
				if (checked == 0) {
					alert(msg);
					radio[0].focus();
					return false;
				}
				break;

			case "select-one":
				if (form.elements[i].selectedIndex == 0) {
					alert(msg);
					form.elements[i].focus();
					return false;
				}
				break;
		   }
		}
		else continue;
	}

	// email
	if (mail.test(form.r_email.value) == false) {
		alert("La dirección de email ingresada no es válida");
		form.r_email.focus();
		form.r_email.select();
		return false;
	}

	return true;
}