Custom error documents not work

[naoki]

Plesk 9.5.2 on Windows 2008 R2 Enterprise 64bit

I've followed this kb article to create custom 404 page:

http://kb.odin.com/en/5279

But always get default IIS 7.5 404 page, you may check it here:

http://www.yangyin1989.com/faaa/

And even in pleask control page, when I try to visit a page not exist, I get a IIS 7.5 error page instead of plesk customized 404 page.

Please advise.