function get_rand()
{
   var rand=Math.round(Math.random()*10);
   while (rand>3) {
      rand=Math.round(Math.random()*10);
   }
   return rand;
}

var imgs=['A_1.jpg','B_1.jpg','C_1.jpg','D_1.jpg'];
var idx=get_rand();
var img_name=imgs[idx];

document.write('<div id="aggrban"  style="width: 222px; height: 79px; border: none; padding: 0; margin: 0; background: transparent; text-align: center;"><a href="http://malayalam.puzha.com"><img src="http://www.puzha.com/puzha/news/images/'+img_name+'" border="0" /></a><br/><span style="font-size: x-small; color: blue;">malayalam.puzha.com</span></div>');