function thumbclick(elem,url)
{
    document.getElementById("big_img").src = url;
    var allThumbs = elem.parentNode.getElementsByTagName('img');
    for(i=0;i<allThumbs.length;i++)
    {
    
       if(allThumbs[i].className.indexOf('active') != -1)
         allThumbs[i].className = 'imgThumb';
    }
    elem.className = 'imgThumb active';
    
}