Why some HTML elements are available as javascript global variables and other elements are not?
Why an input element is visible as global variable only if it is outside of a form?
With this simple page:
<html>
  <body>
    <form id="form1">
      <input id='input1' />
      <div id='div1'></div>
    </form>
  </body>
</html>
I have both div1 and input1 as global variables in Chrome, but in IE10 I input1 is undefined: http://jsfiddle.net/M5ExX/
If I remove the form and leave the div and the input, then both are defined, both in Chrome and in IE: http://jsfiddle.net/M5ExX/1