'Attempts to return the URL to an msapplication square icon with the
passed dimension. If one is not defined, returns None.'

def _check_ms_icon_size(self, dimension):

    selector = ('meta[name="msapplication-square%sx%slogo"]' % (dimension, dimension))
    try:
        return self._document(selector)[0].attrib['content']
    except:
        return None
