Cannot find ContentPlaceHolder 'placeholderBackground' in the master page '/App_Master/mobile.master', verify content control's ContentPlaceHolderID attribute in the content page.
An unhandled exception occurred during 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.Web.HttpException: Cannot find ContentPlaceHolder 'placeholderBackground' in the master page '/App_Master/mobile.master', verify content control's ContentPlaceHolderID attribute in the content page.