Problem: I needed to dynamically change the height/width of a div, but I didn't want to write another few lines of javaScript. Is there a way I can find a pure css solution? you bet! Solution: Thanks to CSS3, we can now do this easily using the calc() function! #myDiv { width: calc(100% - 100px); height: calc(100% - 100px); margin: auto; border: solid 1px #000000; } More good news: It works on all browsers :) Onward! References: http://www.w3schools.com/CSSref/func_calc.asp http://stackoverflow.com/questions/1192783/css-how-to-set-div-height-100-minus-npx