function cascade() {
var nav = document.getElementById("nav");
var navli = nav.getElementsByTagName("li");
	for (var i=0; i<navli.length; i++) {
		navli[i].onmouseover=function(){
			if(this.className != "" && this.className.indexOf("schover") == -1 )
				this.className = this.className + " schover";
			else if((typeof this.className == 'undefined')||(this.className == "")){
				this.className = "schover";
			}
		}
		navli[i].onmouseout=function() {
			var scClass = this.className;
			if(scClass == "schover")
				this.className = "";
		}
	}
}