Too bad they don't dogfood it (source: Default.aspx):

    <div class=mainholder>
    ...
    <div class=sidebar>
    ...
    <div class=maincontent>
    ...
    etc.

Also, the classic (header, 3-col, footer) layout is missing.

e.g.

    HEADER
    ------
    C|C |C
    C|C |C
    C|C |C
    C|C |C
    C|C |C
    ------
    FOOTER