Error: Cannot find inner HTML property of null

Question

in my code there like that ,
<form id=fm ></form>

Answer 1

You can use jQuery Like this:
$('#myform').html();

Answer 2

Where is your JavaScript code?

Answer 3

var elm = document.getElementsByTagName("form");
elm[0].innerHTML = "string";
OR
var elm = document.getElementById("fm");
elm.innerHTML = "string";

Answer 4

m.b. id should be between " or ' symbols?