JavaScript validation demo

<!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>
  <script type="text/javascript">
  <!--
  function validateForm()
  {
  var x=document.forms["myForm"]["fname"].value;
  if (x==null || x=="")
  {
  alert("First name must be filled out");
  return false;
  }
  }
  //-->
  </script>
  <title>JavaScript validation demo</title>
</head>
<body>
  <form name="myForm" action="demo_form.asp" onsubmit="return validateForm()" method="post" id="myForm">
    First name: <input type="text" name="fname" /><input type="submit" value="Submit" />
  </form>
</body>
</html>