A server error occurred in the application.

Loading viewstate failed. The tree of controls to which the viewstate is loaded must match the tree of controls used to save the viewstate during the previous request. For example, when dynamically adding controls, the controls added during the retransmission must match the type and location of the controls added during the initial request.
Description:An unhandled exception occurred while executing the current web request. Please review the stack trace for more information about the error and its origin in the code.

Exception Details:</ font> Contains. Failed to load viewstate. The tree of controls to which the viewstate was loaded must match the tree of controls used to save the viewstate during the previous request. For example, when dynamically adding controls, the controls added during the retransmission must match the type and location of the controls added during the initial request.

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

[HttpException (0x80004005): Failed to load viewstate.  The control tree into which viewstate is being loaded must match the control tree that was used to save viewstate during the previous request.  For example, when adding controls dynamically, the controls added during a post-back must match the type and position of the controls added during the initial request.]
   System.Web.UI.Control.LoadViewStateRecursive(Object savedState) +306
   System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState) +134
   System.Web.UI.Control.LoadViewStateRecursive(Object savedState) +221
   System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState) +134
   System.Web.UI.Control.LoadViewStateRecursive(Object savedState) +221
   System.Web.UI.Control.LoadChildViewStateByID(ArrayList childState) +121
   System.Web.UI.Control.LoadViewStateRecursive(Object savedState) +235
   System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState) +134
   System.Web.UI.Control.LoadViewStateRecursive(Object savedState) +221
   System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState) +134
   System.Web.UI.Control.LoadViewStateRecursive(Object savedState) +221
   System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState) +134
   System.Web.UI.Control.LoadViewStateRecursive(Object savedState) +221
   System.Web.UI.Control.LoadChildViewStateByIndex(ArrayList childState) +134
   System.Web.UI.Control.LoadViewStateRecursive(Object savedState) +221
   System.Web.UI.Page.LoadAllState() +312
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1661

Solution:It may be caching. Clear your browser cache and do a full refresh of your browser and publish if it continues.