[ruslan_mart]

$(function() {
   var banner = $('#banner'), divs = [], rand;

   divs[0] = 'content 1';
   divs[1] = 'content 2';
   divs[2] = 'content 3';

   rand = Math.floor(Math.random() * divs.length);

   banner.html('<div id="container' + (rand + 1) + '">' + divs[rand] + '</div>');
});