Strange Prob With Web.config <<identity> section.

[Sonal]

I am trying to impersonate user with windows account.

If I write following lines in web.config it show error
<identity impersonate="true" userName="contoso\Jane" password="pass"/>

ERROR:
Error while trying to run project: Unable to start debugging on the web
server. Server side-error occurred on sending debug HTTP request.

Make sure the server is operating correctly. Verify there are no syntax
errors in web.config by doing a Debug.Start Without Debugging. You may also
want to refer to the ASP.NET and ATL Server debugging topic in the online
documentation.


On the other hand if i just write like this then error goes aways and
application starts running...

<identity impersonate="true" userName="" password=""/>


I am wondering what is wrong. can any one guide.