Enable IIS Failed Request Tracing

Step 1: Enable windows feature :  Internet Information Services >  World Wide Web Services  > Health and Diagnostic > Tracing

Step 2: Open IIS Manage > Go to your site >  click 'Failed Request Tracing...’ on actions pane > Click 'enable'.

Step 3: In the features view, click 'Failed request tracing rules'.  Click add and choose your purpose like below :

a : Selected ‘All Content (*)’ , Status Code(s) : 200 

b:  Selected ‘ASP.NET (*.aspx) , Staus Code(s) : 401-999 , Event severity : Error

c:  Selected ‘Custome : *.js’ , Status Code(s) : 200

Step 4 : Look in c:\inetpub\logs\FailedReqLogFiles\w3svcX\