Untitled

<html>
<head>
<script>
 function disableSubmit() {
  document.getElementById("submit").disabled = true;
 }

  function activateButton(element) {

      if(element.checked) {
        document.getElementById("submit").disabled = false;
       }
       else  {
        document.getElementById("submit").disabled = true;
      }

  }
</script>
</head>
<body onload="disableSubmit()">
 <input type="checkbox" name="terms" id="terms" onchange="activateButton(this)">  I Agree Terms & Coditions
<br><br>
<input type="submit" name="submit" id="submit">
  </body>
</html>