Some improvements on the feedback popup

* Fix some issues related to the popup display.
* Add max-height attribute to have a better control on the dynamically sized popup. (The max-height is only set is height is not specified)
I'm not sure about what the spec say, but isn't it bad to have an empty element here, like:

    width:100px; height:;max-height:300px;

In my opinion, it would be cleaner to remove those key-value pairs completely. Otherwise, it looks good,.