<!DOCTYPE quirks-mode> <link rel="help" href="https://quirks.spec.whatwg.org/#the-body-element-fills-the-html-element-quirk"/> <link rel="match" href="body-fills-html-quirk-ref2.html" /> <style> html { width: 200px; height: 200px; writing-mode: vertical-lr; } body { border: solid; margin: 10px 11px 12px 14px; } span { display: inline-block; width: 100px; height: 100px; background: green; } </style> <body> <span></span> </body>