difurios, так что именно тебе нужно?
<!DOCTYPE html>
<html>
<head>
<!--
<script src="http://code.jquery.com/jquery-latest.js"></script>
<link rel="stylesheet" type="text/css" href="tmp.css" />
-->
<style type="text/css">
</style>
<script type="text/javascript">
function test(Val,Id) {
var e = document.getElementById(Id);
if (Val!='1800') {
e.style.display = '';
return;
};
if(e.style.display == '')
e.style.display = 'none';
else
e.style.display = '';
}
</script>
</head>
<body>
<div id='txt'>Test</div>
<select name="items" id="gps" onchange='test(this.value,"txt")'>
<option value="2830">Galileo</option>
<option value="1800">Teltonika 1100</option>
<option value="2830";>ADM 600</option>
<option value="0" >Выберите вариант</option>
</select>
</body>
</html>