image = new Array(12);
image [0] = '0'
image [1] = '1'
image [2] = '2'
image [3] = '3'
image [4] = '4'
image [5] = '5'
image [6] = '6'
image [7] = '7'
image [8] = '8'
image [9] = '9'
image [10] = '10'
image [11] = '11'
image [12] = '12'

กกกก number = Math.floor(Math.random() * image.length); 
//<style>body{background-image:url(/images/bbsheader/header.jpg);background-position: center top;background-repeat: no-repeat;}</style>
document.write("<style>body{background-image:url(/images/bbsheader/"+image[number]+".jpg);background-position: center top;background-repeat: no-repeat;}</style>");