var anzahl = 2;
var nr = Math.floor(Math.random()*anzahl);
document.write('<style>#middleColumnS{background-image:url(fileadmin/user_upload/Start/bild' + nr + '.jpg)}</style>')
document.write('<style>#middleColumnS{background-repeat:no-repeat}</style>')
document.write('<style>#middleColumnS{background-position:top right;}</style>')