you can use
<system.webServer>
<handlers accessPolicy="Read, Script">
<add name="ReportViewerWebControlHandler" preCondition="integratedMode" verb="*" path="Reserved.ReportViewerWebControl.axd" type="Microsoft.Reporting.WebForms.HttpHandler, Microsoft.ReportViewer.WebForms, Version=11.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91" />
<add name=".att" path="*.att" verb="*" modules="IsapiModule" scriptProcessor="C:\Windows\Microsoft.NET\Framework64\v2.0.50727\aspnet_isapi.dll" resourceType="File" preCondition="classicMode,runtimeVersionv2.0,bitness64" />
<add name=".htm" path="*.htm" verb="*" modules="IsapiModule" scriptProcessor="C:\Windows\Microsoft.NET\Framework64\v2.0.50727\aspnet_isapi.dll" resourceType="File" preCondition="classicMode,runtimeVersionv2.0,bitness64" />
</handlers>
</system.webServer>