Hi I've written a JavaScript function which changes the value of a form textfield when a tickbox is checked/unchecked.


It works fine in Firefox (Mozilla) but doesn't work in Internet Explorer... Why not?

Here's my code:

Code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Untitled Document</title>
<script language="JavaScript" type="text/javascript">

function UpdateField()
{
if (document.form1.field1.checked==true) {
	document.form1.field.value=1;
}
	else 
		{
		document.form1.field.value=0;
		}
}

</script>
</head>

<body>
<h1>Tickboxes manipulate textboxes</h1>
<form id="form1" name="form1" method="post" action="">
  <input name="field1" type="checkbox" id="field1" value="1"  onchange="UpdateField()" />
  <input type="text" name="field" value="0" />
  &nbsp;
</form>
</body>
</html>