+1  A: 

ddddddddddddddddddddddddddddddddddddddddddddddddddddddd is > 181px.

Its obviously going to overflow because its taken as a single word and words are not broken up. Try using some proper text or give some space like "ddddddddddd ddddddddddddd ddddddddddddddddd dddddddddddddd"

EDIT:

on the other hand the same will happen to images. So anything within the div that is larger than its parent will overflow. you can try using 'overflow:hidden'

Virat Kadaru