1. Change the web.config file as follows:

<handler><add name="ReportViewerWebControlHandler" preCondition="integratedMode" verb="*" path="Reserved.ReportViewerWebControl.axd" type="Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=10.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" /></handler>

i)Name as ReportViewerWebControl to ReportViewerWebControlHandler

ii)version from 9 to10

iii)precodition as integratedMode

 

2. Refresh the portal .