How to maintain the position of the scrollbar on postbacks (across the entire site)
You can just setup the web.config file to reflect this changes all over the site. You can also achieve this on individual page level. But configuring web.config centralizes the configuration and makes your site more manageable and maintainable. Here is the code on the web.config file to preserve the scroll position of the page on post backs.
<pages maintainScrollPositionOnPostBack="true" />