JavaScript KeyCode Values are "undefined" in Internet Explorer 8

Just a hunch, try this:

var keyCode = e.keyCode ? e.keyCode : e.which;

It looks like under IE8 the keyCode property of window.Event is undefined but that same property of window.event (note the lowercase e) has the value. You might try using window.event.

function doSubmit(e)
{
   var keyCode = (window.event) ? e.which : e.keyCode;
   if (keyCode == 13)
      document.getElementById("ctl00_ContentPlaceHolder1_Login").click();  
}

It's worked on this way on my code:

var kcode = (window.event) ? event.keyCode : event.which;