ASP.NET AJAX UpdatePanel control introduced a new mechanism to avoid page flickers during postbacks , while we did gained from this approach we should carefully use the UpdatePanel control.

ASP.NET AJAX was not only introduced to give us a user friendly application but also to provide us with an efficient and performed applications and to minimize the amount of data sent on the wire during postbacks, here am just giving couple of tips to follow while using the UpdatePanel control

Am summarizing here couple of tips you should follow

1-      Whenever using multiple UpdatePanel controls in your page consider setting the UpdateMode property to conditional to minimize the amount of data sent over the wire.

2-      Whenever using the UpdatePanel control try to nest only those controls that will be updated from the server against the pages’ events

3-      Try to avoid using the UpdatePanel control, the only drawback of using this will be including some javascript code, the effort you will introduce in doing so will increase your application's performance.

Consider reading the following articles
UpdatePanel Tips and Tricks
ASP.NET AJAX Architecture

Enjoy J