By default When web pages fire a post back to the server, the browser scroll is returned to the top of the page.
When the page is tall, it is very annoying.
You are three ways to kill this behaviour.

   1. Application level: To set the property by default for all pages in the website, open web.config and add the attribute to the pages node.

      <pages maintainScrollPositionOnPostBack="true">

   2. Page Level: for a particular page, open the aspx and set the property

      <%@ Page MaintainScrollPositionOnPostback="true" >

   3. Code level: to set the property programmatically

      Page.MaintainScrollPositionOnPostBack = true;