var elem = 'TR'; // Object you want to affect: TR or TD

if(document.getElementsByTagName){
var el = document.getElementsByTagName(elem);
for(var i=0; i<el.length; i++){
if(el[i].childNodes[0].tagName != 'TH'
&& el[i].parentNode.parentNode.className.indexOf('tbl') != -1){
if(i%2 == 1){
el[i].className = 'on';
el[i].oldClassName = 'on';
el[i].onmouseout  = function(){
this.className = 'on';
}
} else {
el[i].className = 'off';
el[i].oldClassName = 'off';
el[i].onmouseout  = function(){
this.className = 'off';
}
}
  el[i].onmouseover = function(){
if(this.className == this.oldClassName)
{this.className = 'hover';}
if(this.onmouseout == null && this.className != 'click'){
this.onmouseout = function(){
this.className = this.oldClassName;
}
 }
}
el[i].onclick = function(){
if(this.className != 'click'){
this.className = 'click';
 } else {
this.className = this.oldClassName;
}
this.onmouseout = null;
}
}
}
 }