Css overflow with embeded div and absolute postition?

I tried to do this: http://jsfiddle.net/kritya/wTnEg/

When i click on the 开发者_运维百科div with id add but when it exceeds the class with content-doing it doesnt gets scrollers.

What have i been doing wrong ?

I am getting scroll bars in FF on a mac. The height of the block at 1.5em might just be too narrow to have the scroll bar be of any use. Try making that container a little taller right out of the gate.