use just the last selected item).
<input name="idi" type=text size="15">
<input name="uri" type=text size="45" value="cic:/"><br>
<input type=submit value="add alias"><input type=button value="delete selected" onClick="rimuovialias()";><br>
<input name="idi" type=text size="15">
<input name="uri" type=text size="45" value="cic:/"><br>
<input type=submit value="add alias"><input type=button value="delete selected" onClick="rimuovialias()";><br>
-<select name="elenco" size=7>
+<select name="elenco" multiple size=7>
<script language=Javascript> listalias(); document.aliaslist.idi.focus(); </script>
</select>
<br>
<script language=Javascript> listalias(); document.aliaslist.idi.focus(); </script>
</select>
<br>