int i;
    for (i=0;i<20;i++)
    {
        try {
            Assert.assertTrue(pageSource().contains(banner));
            break;
        }
        catch (Exception e){
            Thread.sleep(5000);
        }
    }

while (!pageSource().contains(banner)) {
    try {
        Thread.sleep(5000);
    } catch (final InterruptedException ie) {
        // log something or whatever
    }
}