var x = 0
var rot
var adimgsrc = new Array();

adimgsrc[11] = "ch1.jpg"
adimgsrc[12] = "ch2.jpg"
adimgsrc[13] = "ch3.jpg"
adimgsrc[14] = "ch4.jpg"

function RndmNum(){
  x = Math.random();
  x = x * 100;
  x = Math.round(x);}
	
while ((x <= 10) || (x > 14)){
  RndmNum();}

rot = '<img src="images/' + adimgsrc[x] + '"width="577" height="181" border="0"></a>'