I am not sure about the issue but I am providing some possibilities:
Possibility 1:
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You set customError mode remote only so if you run the application from your local machine then it won't work perfectly. Because it works with only remote users.
Possibility 2:
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Make sure that redirect url path is correct. Means your 404.aspx is present in ErrorPages folder and path is correct.
Possibility 3:
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You set Statuscode as 404 means it works only when file not found. Means when a user try to browse a file which is not present in correct path in that case it work. Secondly if any others error will happen it redirect to oops.aspx
Possiblilty 4
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If you write any logic in Page_Error, Application_Error then it may not work perfectly. Please recheck it. Secondly you can change redirectMode tag in to to ResponseWrite like:
Manas MohapatraPosted Jul 17, 2015, 2:31 AM
Chinna NethaPosted Jul 17, 2015, 2:07 AM
Manas MohapatraPosted Jul 17, 2015, 12:41 AM
Raja TPosted Jul 17, 2015, 12:35 AM