function showDiv(num){
	var i = 1;
	for (i=0;i<1000;i++){
		if (document.getElementById('c' + i)){
			eval("document.getElementById('c" + i +"').style.display = 'none'");
			eval("document.getElementById('bt" + i +"').className = ''");
			if (i == num) {
				eval("document.getElementById('c" + num +"').style.display = 'block'");
				eval("document.getElementById('bt" + num +"').className = 'on'");
			}
		}
	}	
}