bodyBgs = 
[
 "bg_01", 
 "bg_02", 
 "bg_03"
]
var bodyBg = bodyBgs[Math.floor(Math.random()*bodyBgs.length)]

document.write("<style type=\"text/css\">body{background: #572700 url(/img/" + bodyBg + ".jpg) no-repeat top center !important;}</style>");