צריך עזרה בJS

[BlueNosE]

<script type="text/javascript">

function InputName(){

if (inputname.value == '')
{
 alert('Error!');
 return false;
}
else
return true;

}
</script>

<form action="bla.php" method="post" onsubmit="InputName()">
<input type="text" name="inputname" />
<br />
<input type="submit" name="submit" value="שלח" />
</form>