his test, then the initial containing block's size is used as a fallback which is, in this test, equal to the width of the viewport." />

  <!--

  Inside this batch of 8 sizing-orthog-prct-htb-in-vlr tests:
  001-004: body has 100px margin-left and 100px margin-right
  005-008: body has no horizontal margins

  Inside each sub-batch of 4 tests:
  001-002: containing block's width is 'auto' therefore indefinite
  003-004: containing block's width is 400px therefore definite

  Inside each sub-sub-batch of 2