.left {
	background-attachment: fixed;
	background-image: url(../imagenes/left-margin.gif);
	background-repeat:    repeat;
	background-position: right top;
}
.right {

	background-attachment: fixed;
	background-image: url(../imagenes/right-margin.gif);
	background-repeat:   repeat;
	background-position: left top;
}