if (document.images) {
var b001on = new Image();
b001on.src = "img/chm_still_inv.gif";
var b001off = new Image();
b001off.src = "img/chm_still.gif";
}

function an(imgName) {

            if (document.images)  {

              document[imgName].src = eval(imgName + "on.src");

            }

}



function aus(imgName) {

            if (document.images)  {

              document[imgName].src = eval(imgName + "off.src");

            }



}