How do I change the ID of a HTML element with JavaScript?

Question

I am modifying the ID of an HTML div element client side with JavaScript. The following code works OK in Internet Explorer but not in Firefox/2.0.0.20. It does work in more recent versions of Firefox.

document.getElementById('one').id = 'two';

Can anyone tell me:

1. Why this doesn't work in FireFox.
2. How to make this work in FireFox.

To clarify, I'm changing the element ID to reference a different style in an external style sheet. The style is applied in IE but not in FF.

Answer 1

It does work in Firefox (including 2.0.0.20). See http://jsbin.com/akili (add /edit to the url to edit):

<p id="one">One</p>
<a href="#" onclick="document.getElementById('one').id = 'two'; return false">Link2</a>

The first click changes the id to "two", the second click errors because the element with id="one" now can't be found!

Perhaps you have another element already with id="two" (FYI you can't have more than one element with the same id).