var rolloveron = new Array();
    var rolloveroff = new Array();
    var isIE, isN6;
	
	if (document.all) {		
        isIE = true;	
    }		
    if (document.getElementById && !document.all) {		
        isN6 = true;	
    }
    
	function preloadImages() {
	 //preload images
	 	var i = 0;
		for (i=0; i <= 13; i++)  {
			rolloveron[i] = new Image();
			rolloveroff[i] = new Image();
		}
    		rolloveroff[0].src = "../../../imagenes/BT/voloff.gif";
		rolloveroff[1].src = "../../../imagenes/BT/volsoff.gif";
		rolloveroff[2].src = "../../../imagenes/BT/seccoff.gif";
		rolloveroff[3].src = "../../../imagenes/BT/temasoff.gif";
		rolloveroff[4].src = "../../../imagenes/BT/consoff.gif";
		rolloveroff[5].src = "../../../imagenes/BT/indoff.gif";
		rolloveroff[6].src = "../../../imagenes/BT/ciroff.gif";
		rolloveroff[7].src = "../../../imagenes/BT/eventoff.gif";
		rolloveroff[8].src = "../../../imagenes/BT/glosoff.gif";
		rolloveroff[9].src = "../../../imagenes/BT/publoff.gif";
		rolloveroff[10].src = "../../../imagenes/BT/librooff.gif";
		rolloveroff[11].src = "../../../imagenes/BT/chatoff.gif";
		rolloveroff[12].src = "../../../imagenes/BT/interesoff.gif";
		rolloveroff[13].src = "../../../imagenes/BT/lecturasoff.gif";
		
		rolloveron[0].src = "../../../imagenes/BT/volon.gif";
		rolloveron[1].src = "../../../imagenes/BT/volson.gif";
		rolloveron[2].src = "../../../imagenes/BT/seccon.gif";
		rolloveron[3].src = "../../../imagenes/BT/temason.gif";
		rolloveron[4].src = "../../../imagenes/BT/conson.gif";
		rolloveron[5].src = "../../../imagenes/BT/indon.gif";
		rolloveron[6].src = "../../../imagenes/BT/ciron.gif";
		rolloveron[7].src = "../../../imagenes/BT/eventon.gif";
		rolloveron[8].src = "../../../imagenes/BT/gloson.gif";
		rolloveron[9].src = "../../../imagenes/BT/publon.gif";
		rolloveron[10].src = "../../../imagenes/BT/libroon.gif";
		rolloveron[11].src = "../../../imagenes/BT/chaton.gif";
		rolloveron[12].src = "../../../imagenes/BT/intereson.gif";
		rolloveron[13].src = "../../../imagenes/BT/lecturason.gif";
    	
	}
	/* function: imgChange
	   parameters:  img-> what is the image to change
	                ref-> the new image
	   Description:  Change image img for the new image */

	function imgChange(img,ref) {
	    if (isIE || isN6) {
		    imgOn = eval(ref + ".src");
			document.images[img].src = imgOn;
		}
    }
	window.onload = preloadImages;