var bNNr = new Array() 

bNNr[0] = '<img src="imgs/interiorbanners/rotate/lap_1.jpg" alt="image 1" width="630" height="240" />'

bNNr[1] = '<img src="imgs/interiorbanners/rotate/lap_2.jpg" alt="image 3" width="630" height="240" />'


var a = 0
var b = bNNr.length;

var preBuffer = new Array()
for (z = 0; z < b; z++){
   preBuffer[z] = new Image()
   preBuffer[z].src = bNNr[z]
}

var whichImage2 = Math.round(Math.random()*(b-1));
function randomBnnr(){
document.write('<div>'+bNNr[whichImage2]+'</div>');
}