When using html nested unordered lists in an xhtml document, the error (document type does not allow element "li" here; missing one of "ul", "ol", "menu", "dir" start-tag) is returned from the xhtml validator.(example)<ul> start main list<li> some text </li> <ul> start nested list <li> some text </li> </ul> end nested list<li> some more text </li> </ul> end main list(?) Is there a new way to use nested unordered lists?