see this image this is an example for what am I trying to do with "Waypoints" Class in JQuery.
But it not goes so well.
Here is the link that show what I tried with the Class.
I'm not sure I understood what you asked, but I think you could use an overflow : scroll
with a fixed height on the left div.
I adapted your code so you can see how it looks :
But I think the best solution would be to get rid of the
body {
width:100%;
height:100%;
overflow:hidden;
}
to make the entire body scrollable, and just set the right div as position : fixed
like that :
That will also make your divs more easily scallable to the window's size.
But as I don't exactly know why you need this, I let you choose the best solution for what you need.
Hope I helped you.