function on(imgname) 
{
	if (document.images) {
        regexp = /(\/on\/)+/gi;
        path = document[imgname].src.replace(regexp, "/")
 
        var pathSplit = path.split("/");
        pathSplit[pathSplit.length - 1] = "on/" + pathSplit[pathSplit.length - 1];
        path = pathSplit.join("/");

        // preloading
		var temp = new Image();
		temp.src = path;

		document[imgname].src = path;
	}
}

function off(imgname) 
{
	if (document.images)
        regexp = /(\/on\/)+/gi;
        path = document[imgname].src.replace(regexp, "/")
    
		// preloading
		var temp = new Image();
		temp.src = path;
		
		document[imgname].src = path;
}