$(document).ready(function() {
var randomImages = ['bg_1', 'bg_2', 'bg_4', 'bg_5', 'bg_6'];
	var rndLength = randomImages.length - 1;
	var rndNum = Math.ceil(Math.random() * rndLength);
	$("body").css({ background: "#000 url(/_Resources/img/" + randomImages[rndNum] + ".jpg) fixed no-repeat" });
});