3 common ASP.Net AJAX mistakes

Source: http://encosia.com/2007/10/24/are-you-making-these-3-common-aspnet-ajax-mistakes/

In summary:

• Page_Load executes during every partial postback, same as regular postbacks.
• Use IsPostBack and IsInAsyncPostBack to avoid accidental execution of Page_Load code during partial postbacks.
• In conjunction with __doPostBack, __EVENTTARGET may be used to limit UpdatePanel life cycle event execution to only the targeted panel.
• Control events, such as Click and SelectedIndexChanged, fire after Load events.
  By using PreRender instead of Load, you can allow control events to be handled before your code executes.