function validar(form) {

if ((form.firstname.value == null) || (form.firstname.value=="")) {
 alert("Please enter your first name");
 form.firstname.focus();
 return false;
}

if ((form.surname.value == null) || (form.surname.value=="")) {
 alert("Please enter your Surname");
 form.surname.focus();
 return false;
}

if (!form.sex[0].checked && !form.sex[1].checked){
 alert("Please select your sex");
 return false;
}

if ((form.email.value == null) || (form.email.value=="") || (form.email.value.indexOf("@") == -1)) {
 alert("Please enter a valid address");
 form.email.focus();
 return false;
}	

op = form.country.selectedIndex;
opcion = form.country.options[op].value;
if (opcion=="Not Select") {
   alert('Please select your country');
   return false;
}


if ((form.message.value == null) || (form.message.value=="")) {
 alert("Please enter your message");
 form.message.focus();
 return false;
}

return true;
}