var imagesPreloaded = false;

function imagesPreload() {
	if (document.images) {
		// Noticias
		btNoticiasON 				= new Image();
		btNoticiasON.src 			= "images/empty_bt_on.gif";
		btNoticiasOFF 				= new Image();
		btNoticiasOFF.src			= "images/empty_bt_off.gif";

		// Empresa
		btEmpresaON 				= new Image();
		btEmpresaON.src 			= "images/empty_bt_on.gif";
		btEmpresaOFF 				= new Image();
		btEmpresaOFF.src			= "images/empty_bt_off.gif";

		// Produtos
		btProdutosON 				= new Image();
		btProdutosON.src 			= "images/empty_bt_on.gif";
		btProdutosOFF 				= new Image();
		btProdutosOFF.src			= "images/empty_bt_off.gif";

		// Servicos
		btServicosON 				= new Image();
		btServicosON.src 			= "images/empty_bt_on.gif";
		btServicosOFF 				= new Image();
		btServicosOFF.src			= "images/empty_bt_off.gif";

		// Contactos
		btContactosON 				= new Image();
		btContactosON.src 			= "images/empty_bt_on.gif";
		btContactosOFF 				= new Image();
		btContactosOFF.src			= "images/empty_bt_off.gif";
	}
	imagesPreloaded = true;			
}	

if(imagesPreloaded == false) {
  imagesPreload();
}