function checkemail(form, id)
{
var field = document.getElementById(id).value;
var filter=/^([\w-]+(?:\.[\w-]+)*)@((?:[\w-]+\.)*\w[\w-]{0,66})\.([a-z]{2,6}(?:\.[a-z]{2})?)$/i
if (filter.test(field))
return true;
else{
alert("Please input a valid email address!")
return false;
}
}