Of course margin-right works, but not the way you think it does. You only have one and that's in the container div which is the main div, everything is inside of it. You can't control elements inside of it that way. If you float the container div to the right you will see the right margin, Right now there is nothing to the right of it close enough to show it.
<div class="hr" style='margin-top:-.8em' ><hr /></div>