function swapCats(tabID) {

	var tabs = document.getElementById("categorytabs").getElementsByTagName("td");
	var divs = document.getElementById("categories").getElementsByTagName("div");
	var numtabs = tabs.length;
		
	for(i=0; i < numtabs; i++) {
		
		if (tabs[i].id == tabID) {
			tabs[i].className = "on";
			divs[i].className = "visible";
		} else {
			tabs[i].className = "off";
			divs[i].className = "hidden";
		}
		
	}

}