j.html

<!DOCTYPE html>
<html>
<head>
  <style>
 body{ margin:0; font-size: 12px; font-family: Arial; }
 </style>
  <script src="jquery-latest.js"></script>
  <script>
    $(document).ready(function () {
//      loadNewScreen("1");
      });
  </script>
        

<script>
function loadNewScreen(newScreen) {
  $("#new-nav").load("structure.php?noheader&screen=" + newScreen);
}
function showText() {
	newScreen=document.forms['frmScreenNo'].elements['txtScreenNo'].value;
	loadNewScreen(newScreen);
}

</script>
</head>
<body>
<div id="new-nav"></div>
<div id='divForm' style='font-size:50px'>
<form id='frmScreenNo' action=''>
<p>
<label for='screenNo'>Screen No: </label>
<input style='font-size:50px' type='text' id='txtScreenNo' /></p>
<p><input type='button' style='font-size:50px' onclick='showText();' value='Show screen' /></p>
</form>
</div>
</body>
</html>