Unhandled exception warning in asax file on IIS

[vasanth.kanna]

Dear All,

For handling session time out i have used the asax for writing log files. I got the IIS event viewer - Application warning saying that unhandled exception occured. The warning message is below. Please help me to fix this issue.

Event occurrence: 1
Event detail code: 0

Application information:
Application domain: /LM/W3SVC/1/Root/test-4-128963175910033750
Trust level: Full
Application Virtual Path: /test
Application Path: c:\inetpub\wwwroot\test\
Machine name: DIG

Process information:
Process ID: 4768
Process name: w3wp.exe
Account name: NT AUTHORITY\NETWORK SERVICE

Exception information:
Exception type: NullReferenceException
Exception message: Object reference not set to an instance of an object.

Thanks,
Vasanth.