strange error , Conflict with script manager

Aug 30, 2008 at 5:34 AM
I use PartialUpdatePanel in a pure sample, it works properly and nice,
then I decided to use it in my application, I do not know what ,but I face to an strange error. when I run my application this error is appear :

The page is performing an async postback but the ScriptManager.SupportsPartialRendering property is set to false. Ensure that the property is set to true during an async postback.

I am confused and do not know what is special in my application cause to conflict with PartialUpdatePaneldo not let it do work properly.

I appreciate any suggestion about this.
Aug 31, 2008 at 5:53 AM
I got it.
it is because of this case in my application web.config file

<xhtmlConformance mode="Legacy"/>