Hi

1-  I've a MasterPage in which only ScriptManager is present and NOT an UpdatePanel...

2- UserControls in which ScriptManagerProxy and UpdatePanel is Present and in this UpdatePanel all the remaining controls are present.

3- On My DropDownList AutoPostBack is true, and 2nd DropDownList is filled using 1st DropDownList Selected value on run time...

4-  One ContentPlaceHolder in Master Page.

Thanks

Nasir Ibrahim