ASP.NET 2.0 has introduced a new interface named IButtonControl under System.Web.UI.WebControls namespace. The properties and methods of this interface can be implemented to make a control behave like a button in a web form. One of the important properties is PostBackUrl. This can be used to post the current page to a different page, in other words, doing cross-page posting.
On a related note, view state related to cross-page posting is stored in a hidden variable named __PREVIOUSPAGE. The target page can refer to the posting page by using Page.PreviousPage property which is also new in ASP.NET 2.0.