I don't think that it is possible simply using
HTML but
you should JSPs
Just keep the two html files as
jsp files and use
say a.jsp & b.jsp .You want to include b.jsp in a.jsp,
In a.jsp add this code were you want to include b.jsp
<jsp:include page="b.jsp" flush="true">
Do not include <HEAD> or <BODY> tags inside b.jsp