PHP - Javascript AJAX System - part THREE

<h3>Seleziona istituto</h3>

<div id="regioni" style="float:left">
    <b>(*)</b> Per ubicazione:<br />
    <select id="selectRegioni" name="regioni" onChange="document.forms[0].codiceScuola.value='';callChild(this.name,this.value)">
        <option value="">Seleziona la regione</option>
        <option value="Abruzzo">Abruzzo</option>
        <option value="Basilicata">Basilicata</option>
        <option value="Calabria">Calabria</option>
        <option value="Campania">Campania</option>
        <option value="Emilia Romagna">Emilia Romagna</option>
        <option value="Friuli Venezia Giulia">Friuli Venezia Giulia</option>
        <option value="Lazio">Lazio</option>
        <option value="Liguria">Liguria</option>
        <option value="Lombardia">Lombardia</option>
        <option value="Marche">Marche</option>
        <option value="Molise">Molise</option>
        <option value="Piemonte">Piemonte</option>
        <option value="Puglia">Puglia</option>
        <option value="Sardegna">Sardegna</option>
        <option value="Sicilia">Sicilia</option>
        <option value="Toscana">Toscana</option>
        <option value="Liguria">Liguria</option>
        <option value="Lombardia">Lombardia</option>
        <option value="Marche">Marche</option>
        <option value="Molise">Molise</option>
        <option value="Piemonte">Piemonte</option>
        <option value="Puglia">Puglia</option>
        <option value="Sardegna">Sardegna</option>
        <option value="Sicilia">Sicilia</option>
        <option value="Toscana">Toscana</option>
        <option value="Trentino Alto Adige">Trentino Alto Adige</option>
        <option value="Umbria">Umbria</option>
        <option value="Valle d'Aosta">Valle d'Aosta</option>
        <option value="Veneto">Veneto</option>
    </select>
    <br />
    <div id="province"></div>
    <div id="comuni"></div>
    <div id="istituti"></div>
</div>
<div>
    <b>(*)</b> Per codice:<br />
    <input type="text" name="codiceScuola" maxlength="10" size="10" style="height:18px">
    <input type="button" value="Cerca" style="width:80px;height:30px" onClick="searchCode(document.forms[0].codiceScuola.value)" />
</div>