function arrowDown(id){

   var arrow =  document.getElementById(  id); 
   
 
   if (arrow){
   
        if (id == "nextBtn")
        {  
            arrow.style.backgroundImage  = "url(./images/Arrowleftdown.png)";
            return;   
        }
        
        if (id == "prevBtn")
        {
            arrow.style.backgroundImage    = "url(./images/arrowrightdown.png)";
            return; 
        }
    }
}

function arrowUp(id)
{

   var arrow =  document.getElementById(  id); 
  
   if (arrow){
        if (id == "nextBtn")
        {  
            arrow.style.backgroundImage    = "url(./images/Arrowleftup.png)";
            return;   
        }
        
        if (id == "prevBtn")
        {
            arrow.style.backgroundImage    = "url(./images/arrowrightup.png)";
            return; 
        }
    }

}