function random_content(){
var mycontent=new Array()
//specify random content below.
mycontent[1]='<div class="hp_bg">'
mycontent[2]='<div class="hp_bg2">'

var ry=Math.floor(Math.random()*mycontent.length)
if (ry==0)
ry=1
document.write(mycontent[ry])
}
random_content()