The reported URL works in FF and not in Safari. The expected behavior in FF is that, after editing the text area, and close the window, it should alert the user whether s/he wants to discard changes. In Safari, the JS code of 'document.j2e.changed()' throws an exception because 'document.j2e' is undefined. The HTML source is incorrect in this case. It looks like <object id="j2e" ... > <param> ... <param> some text here It misses </object> to close the tag. WebKit determines that an HTMLObjectElement is not a docNamedNode (see code in HTMLObjectElement::updateDocNamedItem) because it thinks the object element has child that's text node and with non-whitespace texts. I did further test by closing <object> with </object>, but put some text between, or put a non-param tag between. FF allows 'document.j2e' but Safari doesn't. After chatting with Maciej in IRC channel, he mentioned the rule for HTMLObjectElement was to handle a common error (?) that <embed> element is put between <object> and </object>.
*** Bug 20776 has been marked as a duplicate of this bug. ***
It's unclear how to reproduce this now the website is gone. But also plugins have been removed which suggests this is probably no longer an issue.