onchange su select

[Mega69]

<select onchange="if(this[options.selectedIndex].value=='it') { document.getElementById('itSelect').disabled='false'; } else { document.getElementById('itSelect').disabled='disabled'; }">
<option value="it">it</option>
<option value="com">com</option>
</select>

<select id="itSelect" disabled="disabled">
<option ecc...
</select>