var arrImageNames =["PIC_changer_1.jpg","PIC_changer_2.jpg","PIC_changer_3.jpg","PIC_changer_4.jpg"],        
strImagesPath = "http://siteresources.worldbank.org/INTCROATIA/Images/",        
elChImg;   
     
function initImageRotator() {        
 elImg = document.getElementById("target_img");
 if (elImg) {         
  window.setInterval(changeImage, 3500);      
 }      
}            
function changeImage () {      
 var iIdx = Math.floor(Math.random() * arrImageNames.length);      
 elImg.src = strImagesPath + arrImageNames[iIdx];    
}    


initImageRotator();