title: Prevent content to scroll beneath a fixed navbar
body: <p>This page <a href="http://alsotoday.com/roemerstrasse/" rel="noreferrer">http://alsotoday.com/roemerstrasse/</a> has a fixed bootstrap navbar, which should stay fixed, so the video in the background can shine through it. When scrolling the content all the way up, it will go beneath the navbar, which is not favourable. Anybody know, how to create an upper margin for the content, so it will scroll only just beneath the navbar without changing the navbar to not-fixed?</p>
  
  <p>Edit 1:
  main-area-video and panel_container (meanwhile called main-area) are both height 100%, because each, the video and the tiles should fill a screen.</p>