Here is a simple idea:

  html(
    head(
      title('This is the title')),
    body(
      div(id='header', body=...)))

We could also create a shortcut for div ID and classes.. for instance a keyword capitalized is an ID, or something starting with _ could be a class.

It could then be possible to make "custom" fields:

html( headers(), left_side(), content(), footer())