Is it possible to make DIV bigger when content of the page is scrolled? I have chatbox with position:fixed on the right side of my page. My CSS for the chat box is height:100% right:0 bottom:0 top:50px. The top:50px is because I don't want it to hide the navigation bar on top of my page. Now the problem is, that when I start scrolling the page, the navigation bar obviously disappear from sight and there is 50px high blank space on top of my chatbox. What I want is that when I start scrolling the page, the chatbox should take the whole 100% of the screen, so that there is no blank space on top of it.