Strange, when the 'top' is set to 20px for me, the top 15px are hidden behind the header bar, as highlighted light blue in the picture. 

There are no custom themes being used, and I am using 5.0.10

![image](https://f.cloud.github.com/assets/3472717/1001340/0882ba9a-0a68-11e3-8413-149d214c477b.png)