function verif_formulaire() {

if (document.tx_astaddresszipsearch_pi1.tx_astaddresszipsearch_pi1[DATA][zip].value.length == 1) {

alert ('ok');
return false;

}
if (document.tx_astaddresszipsearch_pi1.tx_astaddresszipsearch_pi1[DATA][zip].value == "") {

alert ('ok');
return false;

}

}