IE 7 will support the hover pseudo class on other elements aside from the anchor tag. So adding td:hover {background: #??????} to the CSS will work on all browsers except IE 6 and previous. Problem is too many people use IE for that alone to be a viable option. Adding the following will make it work without js on a decent browser and with js on IE 6 and less

CSS

td, .jsout {background: #???;}
td:hover, .jshover {background: #???;}

Javascript

function changeBG(){
var bg = document.getElementsByTagName("td");
for (i = 0, j = bg.length; i < j; i++) {
bg.onmouseover=function() {
this.className="jshover";
}
bg.onmouseout=function() {
this.className="jsout";
}
}
}
window.onload=function(){
changeBG();
}