I'm beginning to get frustrated with CSS. Anytime I think I've grasped one of its many facets, I'm completely thrown off by unexpected behaviour.I've been trying to make a sticky footer. SO I set the height of my body element to 100% so it takes up the full html element in height ( browser window ). I then wrap everything inside the body in a div except for the footer element, and set this div's height to 100%, thinking that this will take up the full body in height and so push the footer off the bottom of the screen. I could then apply a negative margin yo bring it up and fix it at the bottom.But the footer sits at the bottom of the page below all the body, without need for a negative margin.. So my idea of setting height to 100% is completely thrown off. What's happened here?