<!DOCTYPE html> <html> <head> <style> @namespace url(test); div { background-color: green; } div[dir=RTL ] {background-color: red !important; } </style> <script> function f() { var elem = document.createElementNS("test","div"); elem.setAttribute("dir","rtl"); elem.appendChild(document.createTextNode("text")); document.getElementsByTagName("body")[0].appendChild(elem); } </script> </head> <body onload="f();"> </body> </html>