Download a file using jQuery after creating it in the server

When I click a button on the client side I want to invoke a public static webmethod on the server side using AJAX. The static method will create the appropriate file. After the file is created I need to download it to the client desktop. I’ve found John Culvinar’s jquery filedownload plugin but haven’t been able to implement it so far. I know that using this plugin also requires writing a cookie so that it knows that the download is complete. Where do I put this code in the server side? After creating the file? I’d be very glad if someone could show me a sample on this scenario, maybe on jsfiddle.net

How to manage DOM elements

I have implemented Infinite scrolling(i.e Load records when the scrollbar reaches the bottom of the div). It works fine but after loading too many records on the page, the page becomes too heavy & causes slow rendering. Actually, I am using this technique as a replacement of a gridview so, how do i manage heavy DOM in this scenario?