http://www.asp.net/ajax/documentation/live/tutorials/IntroductionUpdatePanel.aspx

http://www.asp.net/AjaxLibrary/AjaxControlToolkitSampleSite/UpdatePanelAnimation/UpdatePanelAnimation.aspx

If you wants to update the partcular content of web page instead of whole web page at that time you can simple put the content in update pannal along with timer controll so whenever the timer controll set time is triggred at that time update pannel content automatically refreshed.. for e.gput the gridview in update pannel and call the gridview.databind() function on Timer_tick . you wiill observe that the gridview content only be updated instead of whole page

If you want to refresh only the part of the page instead of refreshing the entire page we can use update panel.