Åpne en modal dialogboks med JavaScript

<script type="text/javascript" language='JavaScript'><!--
<!--
//Lager en funksjon
function OpenNewWindow()
{
 if(window.showModalDialog)
 {
     window.showModalDialog('js_modal.html', window)
 }
 else
 {
     alert('This method is only supported by Internet Explorer 4 and above.')
 }
}
//-->
</script>

<form><INPUT TYPE="button" VALUE="Åpne vindu" onClick="OpenNewWindow();"></form>