How to error in manage

i have designed web application in asp.net...i have publish a website.. i have create virtual directory and copy the publish file.... and browse the website...

The error r occure

Object reference not set to an instance of an object. Description: An unhandled exception occurred dur开发者_JS百科ing the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

To see the actual details about the error, You have to set customErrors mode="Off" in the web.config

<customErrors mode="Off" defaultRedirect="error.aspx"> 
  <error statusCode="404" redirect="ileNotFound.htm"/> 
</customErrors>

If you are able to get the details of error, then you will know where the problem is and then you will be able to fix it.