How to Make the Scrolling of div tag move to top

How to Make the Scrolling of div tag move to top

i am making the chat in PHP and Ajax i want that the scrolling will move top and the user can view the currect msg... please suggest..

Bye

this is the working solution for chat based Div ...

function scrooldown(div){
var scrollDiv = document.getElementById(div);
scrollDiv.scrollTop = scrollDiv.scrollHeight;
scrollDiv = null;
}