slide down slide up javascript coding

[Geevaa]

availheight= document.getElementById("div1").clientHeight;
document.getElementById("div1").style.height="0px";
document.getElementById("div1").style.overflow="hidden";
document.getElementById("div1").style.visibility="visible";
function expand(ele,currentheight){
currentheight+=5;
document.getElementById(ele).style.height=currentheight
+"px";
if(currentheight < availheight){
setTimeout("expand('"+ele+"',"+currentheight+")",
50);
}
}
function collapse(ele,currentheight){

currentheight-=5;

document.getElementById(ele).style.height=currentheight
+"px";
if(currentheight > 0){
setTimeout("collapse('"+ele+"',"+currentheight+")",
50);
}
}