window.onload=function(){
		var lastDiv = "";
		document.getElementById('SndSecondCombo').onchange=function(){
		if (lastDiv)
		document.getElementById(lastDiv).className = "hiddenDiv";
		//if value of the box is not nothing and an object with that name exists, then change the class
		if (this.value && document.getElementById(this.value)) {
		document.getElementById(this.value).className = "visibleDiv";
		lastDiv = this.value;}}}