'Asserts that two HTML snippets are not semantically equivalent.'

def assertHTMLNotEqual(self, html1, html2, msg=None):

    dom1 = assert_and_parse_html(self, html1, msg, u'First    argument    is    not    valid    HTML:')
    dom2 = assert_and_parse_html(self, html2, msg, u'Second    argument    is    not    valid    HTML:')
    if (dom1 == dom2):
        standardMsg = (u'%s    ==    %s' % (safe_repr(dom1, True), safe_repr(dom2, True)))
        self.fail(self._formatMessage(msg, standardMsg))
