var bg = new Array(); bg[bg.length]='https://nsa15.casimages.com/img/2010/03/16/100316053300460401.png'; bg[bg.length]='https://nsa14.casimages.com/img/2010/03/16/100316051937790710.png'; bg[bg.length]='https://nsa14.casimages.com/img/2010/03/16/100316052044640342.png'; bg[bg.length]='https://nsa14.casimages.com/img/2010/03/16/100316052112927309.png'; document.body.style.backgroundImage='url('+bg[Math.floor(Math.random()*bg.length)]+')';