Modify SharePoint web.config to display error details

Enable Custom Errors: Set the customErrors mode to “Off”

Find: <customErrors mode=”On” />

Change to: <customErrors mode=”Off” />

Enable the Call Stack Trace: Set the CallStack value of the SafeMode element to “true”

Find: <SafeMode … CallStack=”false” … >

Change to: <SafeMode … CallStack=”true” … >

Enable Debugging Mode: Set batch and debug to “true”

Find: <compilation batch=”false” debug=”false”>

Change To: <compilation batch=”true” debug=”true”>