nextgen pro horizontal filmstrip moves up as browser narrows

It appears that various elements are having their height set dynamically via javascript, when the viewport width changes. This would probably override any css settings you’ve set. Looking at the code, there’s an embedded iframe, within which there’s javascript like this:

var calculateHeight = function (settings) { ...

The code then calculates a height to use based on the viewport width. You’ll need to look at disabling/modifying that javascript.