function img_rollover(img){
	var dot = img.src.lastIndexOf(".");
	var ext = img.src.substr(dot);
	
	var temp = img.src.substr(0, dot); 
	var underscore = temp.lastIndexOf("_");
	var dir = temp.substr(underscore + 1);
	if(dir == "up")
		var src = temp.substr(0, underscore) + "_down" + ext;
	else
		var src = temp.substr(0, underscore) + "_up" + ext;
	
	try{
		img.src = src;
	}
	catch(e){}
}