Try the following code in FireFox.

<div id="div">
<textbox value="Jerry" width="150px" id="test" onOK="test.visible=false; div.invalidate();"/>
</div>

Hitting enter in the textbox will cause an error in FF as:

Failed to mount: Component returned failure code: 0x80004005
(NS_ERROR_FAILURE)
[nsIDOMHTMLInputElement.setSelectionRange