var factsImg = new Array(
      '/images/HippoFacts/atlantic.gif',
      '/images/HippoFacts/breakwind.gif',
      '/images/HippoFacts/captivity.gif',
      '/images/HippoFacts/fastest.gif',
      '/images/HippoFacts/night.gif',
      '/images/HippoFacts/nuggetscorn.gif',
      '/images/HippoFacts/ticklish.gif',
      '/images/HippoFacts/underneath.gif',
      '/images/HippoFacts/bones.gif',
      '/images/HippoFacts/cracker.gif',
      '/images/HippoFacts/migration.gif',
      '/images/HippoFacts/sexiest.gif');
      
var intveralId;
var inTesting = false;
                 
function setRandomHippoFactImg() {
    var randomIndex = get_random();
    if (randomIndex < 0)
        randomIndex = 0;
    if (randomIndex > factsImg.length)
        randomIndex = factsImg.length-1;    
    if (intveralId != null)
        clearInterval(intveralId);       
    var img = document.getElementById('imgHippoFact');
    if (img != null) {        
        img.src = factsImg[randomIndex];    
    }
    else
       intveralId = window.setInterval(setRandomHippoFactImg, 5); // re-try until found    
}

function get_random() {
    var ranNum= Math.floor(Math.random()*factsImg.length);
    return ranNum;
}