css width height not working

sometimes you may find that css width height does not working for html tag b, span,div i came across it also i set the position: absolute, then it do work well below is my css, you can test .loading { left: 25px; position: absolute; top: 20px; background-image: url(“./Resources/loading.gif”); overflow: hidden; height: 40px; width: 40px; background-repeat: no-repeat; }