what is the use of scriptmanager

Kindly refer following link
http://msdn.microsoft.com/en-us/library/bb398863.aspx

Rajesh Patel
MCPD,MS
Brainbench (Asp.Net 4.0 and CSS 3.0)

Sumasri,

Scriptmanger is compulsory when you are using an ajax control in your page or asp.net update panel in your page. <Script> can be used if you are developing a very small application which does not deals with ajax or updatepanel.

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www.flickr.com/photos/psdesigner/

look at this url

http://www.asp.net/ajax/documentation/live/overview/ScriptManagerOverview.aspx
.