$(document).ready(function() {
  if($('#home .bg')) {
    var images = new Array();
    images[0] = 'images/homebgs/1.jpg';
    images[1] = 'images/homebgs/2.jpg';
    images[2] = 'images/homebgs/3.jpg';
    images[3] = 'images/homebgs/4.jpg';
    var random = Math.random() * images.length;
    randomNumber = Math.floor(random);
    $('#home .bg').css('background','url('+images[randomNumber]+')');
  }
});