<html> <head> <style> .lr { -webkit-writing-mode: vertical-lr; background-color:green; margin:10px; width:100px; height:100px; } .float { width:100px; height:100px; background-color:blue; float:left} body { margin: 0 } </style> </head> <body> The green LR block should avoid the blue float. <div class="float"></div> <div class="lr" id="test"></div> <div id="console"></div> <script> if (window.testRunner) window.testRunner.dumpAsText(); test = document.getElementById("test"); rect = test.getBoundingClientRect(); if (rect.left != 100) { document.getElementById('console').innerHTML = "FAIL: The floating block should be at an x-offset of 100."; test.style.backgroundColor = 'red'; } else document.getElementById('console').innerHTML = "PASS: The floating block is in the correct position."; </script> </body>