Enable error viewing in SharePoint
If you faced an unknown error in SharePoint, I am sure that it will not be your happiest moment. To know what is the real error to be able to solve it you have to change 2 options in web.config of the web application that hosts your site. 1-Open web.config 2- Change customErrors mode="on" to customErrors mode="off" 3- Change CallStack="false" to CallStack="true" And wishing you a happy debugging.