.aspx cause redirect but not other extensions

Question

im using asp.net 4.0 integrated mode and im having problems with error redirection. Im trying to redirect 404 errors to another page.

"www.easycomputerformat.com/test.aspx" successfully redirects to 404Error.aspx

but

"www.easycomputerformat.com/test" doesnt.

Doesnt integrated pipeline mean all requrest go throu asp.net?

Thanks.