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 470x19
          text run at (0,0) width 470: "Three green 16x16 pixel squares should appear below, stacked vertically."
      RenderBlock {DIV} at (0,20) size 18x18 [bgcolor=#FF0000] [border: (1px solid #000000)]
        RenderImage {IMG} at (1,1) size 16x16
        RenderText {#text} at (0,0) size 0x0
      RenderBlock (anonymous) at (0,38) size 800x36
        RenderPartObject {IFRAME} at (0,0) size 18x18 [bgcolor=#FF0000] [border: (1px solid #000000)]
          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
        RenderBR {BR} at (18,18) size 0x0
        RenderPartObject {IFRAME} at (0,18) size 18x18 [bgcolor=#FF0000] [border: (1px solid #000000)]
          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
