codice:
<script type="text/javascript">
	var lastType = "";
	function changeAction(type) {
		if(type=='status') {
			
			if(document.status.Uni.value == '') {
				alert('NO SERVER SELECTED !');
			} else {
				var url = "http://" + document.status.Uni.value;
				document.status.action = url;
				document.status.Uni.value = '';
			}			
			
		} else {
			if(document.formular.Uni.value == '') {
				alert('NO SERVER SELECTED !');
			} else {
				var url = "http://" + document.formular.Uni.value;
				var n = new Date();
				document.formular.antiback.value=n.getTime();
				document.formular.action = url;
			}
		}
	}
</script>

<form action="" method="POST" name="formular" target="_top" onsubmit="changeAction('login');">
	<table width=906 align="center" cellpadding="0" cellspacing="0">
		<tr>
			<td width="53" background="vendetta/img/left_bg.jpg"></td>
			<td valign=top>
				<table width="799" border="0" cellspacing="0" cellpadding="0" height="100%">
                			<tr>

                    				<td background="vendetta/img/login_bg_left.jpg" height="63" width="175"></td>
                    				<td background="vendetta/img/login_bg.jpg" height="63" width="449" align="center">



<select name="Uni" class="loginbox" size=1>
<option value=s1.vendetta1923.it/vendetta/login.php>Server1</option><option value=s2.vendetta1923.it/vendetta/login.php>Server2</option><option value=s3.vendetta1923.it/vendetta/login.php>Server3</option><option value=s4.vendetta1923.it/vendetta/login.php>Server4</option><option value=s5.vendetta1923.it/vendetta/login.php>Server5</option><option value=s6.vendetta1923.it/vendetta/login.php>Server6</option></select>

		    			<input type=hidden name="layout" value=1>

						<input type=hidden name="antiback" id="antiback" value=1190153061 >
               			<input type=text name="ln" value="" size=10 maxlength=30 class="loginbox">
						<input type=password name="pw" value="" size=10 maxlength=30 class="loginbox">
               			<input type=image src="vendetta/img/login_bt.jpg" width="50" height="16">
						

			   						    			<font class="content_text" style="font-size: 0.7em;">Con il mio login accetto i Termini d`utilizzo</font>
                    				</td>
</form>
Ecco il codice della form, e ho messo anche il pezzo di script, non sò forse potrebbe dipendere proprio da qualcosa nello script... grazie per l'interessamento