Background not showing behind floating divs [duplicate]

Answer 1

I think you have to give #right_b also a minimal height:

#right_b{
 background:transparent url('img/right.png');
 background-position: right top;
 background-repeat: repeat-y;
 min-height: 30px;
}

Float elements are took out of the normal document flow, so if an element does not contain other "normal" elements, this element has a height of 0 (as it has no content).