var Images = new Array() 

Images[0] = 'sub_content_img_01.jpg'
Images[1] = 'sub_content_img_02.jpg'
Images[2] = 'sub_content_img_03.jpg'
Images[3] = 'sub_content_img_04.jpg'
Images[4] = 'sub_content_img_05.jpg'
Images[5] = 'sub_content_img_06.jpg'
Images[6] = 'sub_content_img_07.jpg'
Images[7] = 'sub_content_img_08.jpg'
Images[8] = 'sub_content_img_09.jpg'
Images[9] = 'sub_content_img_10.jpg'
Images[10] = 'sub_content_img_11.jpg'

var j = 0
var p = Images.length;

var preBuffer = new Array()

	for (i = 0; i < p; i++){
	   preBuffer[i] = new Image()
	   preBuffer[i].src = Images[i]
	}

var whichOne = Math.round(Math.random()*(p-1));