Piotyras

Found the solution myself.
I used this Custom CSS for https://www.vitsi.dk:

Note: THE IMPORTANT ASPECT:
#wrapper padding must be the same value as #footer height!

#wrapper {
  background: none repeat scroll 0 0 #ffffff;
  box-sizing: border-box;
  min-height: 100%;
  padding: 0 0 190px;
  position: absolute;
  width: 100%;
}
#main {
  height: 100%;
  margin: 0;
  padding: 0;
}
#footer {
  background-color: #313131;
  color: #747474;
  bottom: 0;
  left: 0;
  height: 190px;
  position: absolute;
  width: 100%;
}

I thank you very much for your help!