Custom scrollable div
Just focusing on the Javascript:


I feel a urge to to reference a story about a monk. Instead I'll just say that descriptive names will help when you come back to your code or when others try to read it.
for example:

var obj = document.getElementById(id);
obj.style.position = "absolute";
obj.onmousedown = function () {
    scr = obj;
}


Here it would be better to name obj something like draggableElement or some such. this was I know instantly what we are referring to.  
You are testing e and pageY and assigning a variable in two different way. Pick one way and be consistent about it. It really matters not what you choose so much as sticking to it.

Here are a couple of different ways you could do it.


if

if (!e) e = window.event;
var y = e.pageY;
if(!y) y = e.clientY;

ternary

e = e ? e : window.event;
var y = e.pageY ? e.pageY : e.clientY;

or 

e = e || window.event;
var y = e.pageY || e.clientY;



I personally favour this last way.