Question : UpdatePanel sends enter page back?

I've read that the asp.net (3.5) UpdatePanel sends the entire page back on postback.  How can I verify this?

If I want the UpdatePanel functionality without sending back the entire page, would I need to create my own AJAX async and an HTML server side DIV tag to hold everything or just go with a regular Panel?  I want to create a CustomPanel that is basically an UpdatePanel but only renders what's in the panel on async calls.

Answer : UpdatePanel sends enter page back?

red the following link - you will find some good discussion about update panels - it might be helpful
http://stackoverflow.com/questions/72541/one-update-panel-vs-multiple-update-panels