javascript: random image selected on refresh

How about:

HTML:

<img id="image" />

JS:

var description = [
  "http://static.ddmcdn.com/gif/lightning-gallery-17.jpg",
  "http://static.ddmcdn.com/gif/lightning-gallery-18.jpg",
  "http://static.ddmcdn.com/gif/lightning-gallery-19.jpg",
  "http://static.ddmcdn.com/gif/lightning-gallery-20.jpg",
  "http://static.ddmcdn.com/gif/lightning-gallery-21.jpg"
];

var size = description.length
var x = Math.floor(size*Math.random())
document.getElementById('image').src=description[x];

No jQuery necessary.

http://jsfiddle.net/mohammadAdil/SvswX/

<img id='random'/>

script -

var image = new Array ();
image[0] = "http://placehold.it/20";
image[1] = "http://placehold.it/30";
image[2] = "http://placehold.it/40";
image[3] = "http://placehold.it/50";
var size = image.length
var x = Math.floor(size*Math.random())

$('#random').attr('src',image[x]);