Server Error in '/' Application.
Description: An application error occurred on the server. The current custom error settings for this application prevent the details of the application error from being viewed remotely (for security reasons). It could, however, be viewed by browsers running on the local server machine.
Details: To enable the details of this specific error message to be viewable on remote machines, please create a <customErrors> tag within a "web.config" configuration file located in the root directory of the current web application. This <customErrors> tag should then have its "mode" attribute set to "Off".
Above error describes to set Off <customErrors>tag in webconfig file. If you want to see exact error of the page you must turn Off custom error mode. After changing the webconfig file save and reload the page you can view the exact error of the page. This setting is under<system.web>.
<customErrors mode="Off" />