OK, here is another one.

You dinamically create a checkbox and then put its state to checked. Then, you append your new checkbox to its parent. In firefox there’s nothing wrong with that. But Internet Explorer DOES NOT check the box. Why? Well, FIRST you have to show the checkbox and THEN check it.

So:

    chk = document.createElement('INPUT')
    chk.type='checkbox'
    chk.checked=true
    document.getElementById('container').appendChild(chk)

Does not work in IE. You have to rewrite this as:

    chk = document.createElement('INPUT')
    chk.type='checkbox'
    document.getElementById('container').appendChild(chk)
    chk.checked=true