You may come across the above error while configuring and deploying SQL Server Reporting Services. Complete error will look like
Error: Could not load file or assembly 'Microsoft.ReportViewer.Common, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified
Problem: You are missing the installation and configuration info for ReportViewer
Solution: Check the following things
1. Have you installed the Report Viewer? If not you need to download and install it from Microsoft using this link
http://www.microsoft.com/downloads/details.aspx?FamilyID=a941c6b2-64dd-4d03-9ca7-4017a0d164fd&displaylang=en
2. Reboot the Machine on which you installed the Report Viewer
3. Make sure that following configuration is added in your web.config file
<system.web>
<httpHandlers>
<add path="Reserved.ReportViewerWebControl.axd" verb="*" type="Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" validate="false" />
</httpHandlers>
</system.web>