<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html lang="en-US"> <head> <title>Absolute positioning margin:auto regression</title> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <meta http-equiv="Content-Style-Type" content="text/css"> <style type="text/css"> body > div { position: relative; border: medium solid; width: 600px; padding-bottom: 0.5em; } body > div > div { background: blue; width: 400px; height: 1em; margin-left: 100px; } </style> </head> <body> <div> This div should be centered within its container: <div></div> </div> </body> </html>