Could not load file or assembly 'Microsoft.ReportViewer.WebForms, Version=9.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.

                                         You will get this error when the Report viewer installed incorrectly or missing in the system










Solution :     
Download the Report Viewer installer from below link and this will fix the error

Report viewer 2008 installer link

http://www.microsoft.com/en-us/download/confirmation.aspx?id=6576