In listing 12 in the tutorial, the <lift:TD.list> should be inside the <div id="all_todos"> so that upon ajax re-draw the div doesn't get duplicated.

See also the discussion:
http://groups.google.com/group/liftweb/browse_thread/thread/2fb6bad85f6906d8/517d357355146566?lnk=raot#517d357355146566