I am using Asp.net 4.0 chart control while running the application I had faced this error “Error executing child request for ChartImg.axd.”. This problem was resolved by adding chatImageHandler in the webconfig.
<system.webServer>
<validation validateIntegratedModeConfiguration="false"/>
<handlers>
<remove name="ChartImageHandler"/>
<add name="ChartImageHandler" preCondition="integratedMode" verb="GET,HEAD,POST" path="ChartImg.axd" type="System.Web.UI.DataVisualization.Charting.ChartHttpHandler,System.Web.DataVisualization, Version=4.0.0.0, Culture=neutral,PublicKeyToken=31bf3856ad364e35"/>
</handlers>
</system.webServer>
<system.web>
<httpHandlers>
<add path="ChartImg.axd" verb="GET,HEAD,POST" type="System.Web.UI.DataVisualization.Charting.ChartHttpHandler, System.Web.DataVisualization, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" validate="false"/>
</httpHandlers>
</system.web>