Javascript Image Rollover

var homeOff = new Image();
homeOff.src = "homeoff.gif";
var homeOn = new Image();
homeOn.src = "homeon.gif";


function act(imgName, action){
if(document.images){
document.images[imgName].src = eval(imgName+action+".src");
}
}

<img src="homeoff.gif" name="home">

<a href="..." onMouseOver="act("home","On");" onMouseOut="act('home', 'Off');">