WordPress 404 error pages not displaying in IE 8

Chalk this up to yet another reason to hate on Internet Explorer. IE 8 has at least three points of failure for your custom error pages. It will display its own error pages instead of yours if:

• Your error page is under 512 bytes
• The user has “friendly HTTP error messages turned off.” Some claim this is the default setting, it wasn’t in my installation.
• Internet Explorer just doesn’t feel like showing it. No, seriously. Sometimes it works, sometimes it doesn’t with the exact same setup.

Thanks to WPCanada, I was able to force the browser to recognize my custom 404 page by adding this code to the very top of 404.php: