I have a problem in setting the chartHttpHandler in web.config for windows azure

Initially I added a chartHttpHandler on my web.config file

<remove name="ChartImageHandler"/>
<add name="ChartImageHandler" preCondition="integratedMode" verb="GET,HEAD" path="ChartImg.axd" type="System.Web.UI.DataVisualization.Charting.ChartHttpHandler, System.Web.DataVisualization, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/> 

under system.webServer section

Then I got an error stating

Invalid temp directory in chart handler configuration [c:\TempImageFiles\].

Then I found that I should change in

From   
<add key="ChartImageHandler" value="storage=file;timeout=20;dir=c:\TempImageFiles\;" />

To
 <add key="ChartImageHandler" value="storage=file;timeout=20;" />

I am not able to find this section in my web.config file. So I tried to add it under section but it gave me error that it is an invalid child Likewise, I tried adding it under section, it too gave the same error...

So, I added sepeartely, Then I am not able to see anything.. The webpage is just blank...

What should I have to do.. Can anyone tell me "how to solve it"