c# - IIS 6 : CustomError Redirecting Values to avoid? -

i'm trying catch different httperror check causing trouble in .net application.

actually, here customerror contains on application :

 <customerrors mode="remoteonly" defaultredirect="~/error.htm">     <error statuscode="400" redirect="~/errorpage400.htm" />     <error statuscode="401" redirect="~/errorpage401.htm" />     <error statuscode="403" redirect="~/errorpage403.htm" />     <error statuscode="404" redirect="~/errorpage404.htm" />     <error statuscode="408" redirect="~/errorpage408.htm" />     <error statuscode="500" redirect="~/errorpage500.htm" />     <error statuscode="503" redirect="~/errorpage503.htm" />   </customerrors> 

the thing got redirected on page : https://support.microsoft.com/en-us/kb/318380/fr

is kind of default redirection?

this causing trouble application because page embedded in "uncloseable" window. on error pages, got button allows user close page since i'm not redirected on 1 of pages, can't click on it.

if check page,i can see there no 408 error code iis 5 or 6. why it's causing trouble? guess i'd know if knows exact reason