function email(formu)
{
var s = document.form_gusers.gusers_mail.value;
var filter=/^[A-Za-z][.A-Za-z0-9_]*@[A-Za-z0-9_]+\.[A-Za-z0-9_.]+[A-za-z]$/;
if (s.length == 0 ) return true;
if (filter.test(s))
return true;
else
alert("invalid email address");
document.form_gusers.gusers_mail.focus();
return false;
}