questo script che mi autocompleta in base all'input
con internet explorer funziona mentre con firefox no qualcuno sa aiutarmi?

codice:
 <script src="../../programmi/scriptaculous/lib/prototype.js" type="text/javascript"></script> 
<script src="../../programmi/scriptaculous/src/scriptaculous.js" type="text/javascript"></script> 
 <form  action=""  style="margin:0;padding:0;"> 
<input style="font-size:10px; font-family:'Trebuchet MS', Arial, Helvetica, sans-serif; border:solid 1px #000;" type="text" value="Cerca Amici" name="cerca" onFocus="if(this.value==this.defaultValue)this.value=''" onBlur="if(this.value=='')this.value=this.defaultValue"> 
</form> 
<div id="suggest"></div>  
<script type="text/javascript">  
new Ajax.Autocompleter("cerca", "suggest", "../../programmi/cerca_utente.php", {minChars: 1});  
</script>