If you put rubbish in you get rubbish out
Your content div has a height of 250px, yet the parent which is #contentWrapper only has a height of 225px - so what's a browser to do?
Ie decides to expand the elemnt to accomodate your mistake while other browers decide that they will do what you said and keep the parent to 225px height and ignore the overflow. This is where the difference comes form.
Just remove the height and adjust the padding instead.
9 times out of 10 if you tell the browser to do something that makes no sense then the resluts are bound to be unreliable
padding:25px 15px 15px 20px;