Report Viewer Configuration error - In View Source of webpage

I found the following error message when I checked View source of the web page , but the web page works just fine. Our Test lead found the error while performing Assertion tests.

Report Viewer Configuration Error:

The Report Viewer Web Control HTTP Handler has not been registered in the application's web.config file. Add

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

to the system.web/httpHandlers section of the web.config file, or add

<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" />

to the system.webServer/handlers section for Internet Information Services 7 or later

Why is this error message coming up in view source..

Note: There is a div tag around this error message which has style="display:none"

I am trying to find out why but everybody has only discussed this error message as one which is thrown in the webpage. The changes suggested to web.config are already present in our config file.