var province = [ ["084", "AGRIGENTO", "19"], ecc
var comuni = [ ["28001", "ABANO TERME", "028"], ecc
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<select name="DropDowbList_province" id="DropDownList_province" style="width:200px;" onchange="return DropDownList_province_onchange(this)">
<option value="">Seleziona Provincia</option>
</select>
<select name="comuni" id="DropDownList_comuni" style="width:200px;" onchange="return DropDownList_comuni_onchange(this)">
<option value="">Seleziona Comune</option>
</select>
<input type=hidden name=dati value=1>
<input type="submit" name="submit" value="Continua" />