What I'm trying to do is to have 4 expandable divs overlapping each other with transition set in css for 0.6s. Because the expanding lasts for 0.6s I'd like to have the expanded div lose it's higher z-index after it's done collapsing, otherwise it looks silly. However, it doesn't work, the z-index remains unchanged. It's probably somethings stupid, but I just can't find it. Thanks! <div class="wrapper" style="position: relative;"> <div id="one" style="position: absolute;" onmouseover=" this.style.height='250px'; this.style.zIndex='1'; " onmouseout=" this.style.height='50px'; setTimeout(function() {this.style.zIndex='0';},600); ">blahblahblahblah</div> <div id="two" style="position: absolute;" onmouseover=" this.style.height='250px'; this.style.zIndex='1'; " onmouseout=" this.style.height='50px'; setTimeout(function() {this.style.zIndex='0';},600); ">blahblahblahblah</div> </div>