layer at (0,0) size 800x600
  RenderView at (0,0) size 800x600
layer at (0,0) size 800x600
  RenderBlock {HTML} at (0,0) size 800x600
    RenderBody {BODY} at (0,0) size 800x600
      RenderBlock {DIV} at (0,0) size 800x20
        RenderText {#text} at (0,0) size 456x19
          text run at (0,0) width 456: "Two green 16x16 pixel squares should appear below stacked vertically."
      RenderBlock {DIV} at (0,20) size 16x16 [bgcolor=#FF0000]
        RenderImage {IMG} at (0,0) size 16x16
        RenderText {#text} at (0,0) size 0x0
      RenderBlock (anonymous) at (0,36) size 800x16
        RenderIFrame {IFRAME} at (0,0) size 16x16 [bgcolor=#FF0000]
          layer at (0,0) size 16x16
            RenderView at (0,0) size 16x16
          layer at (0,0) size 16x16
            RenderBlock {HTML} at (0,0) size 16x16
              RenderBody {BODY} at (0,0) size 16x16
                RenderImage {IMG} at (0,0) size 16x16
        RenderText {#text} at (0,0) size 0x0