// function to switch the image source of a image
function change_img_src(id, file)
{
  var image = document.getElementById(id);
  if(image)
  {
    // in case of IE < than version 7 special care need be taken for png images
	  if(browser.isIE && browser.version >= 5.5 && browser.version < 7)
    {
      if(file.substr(file.length-3,file.length-1)=='png')
	      image.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = file;
      else
        image.src = file;
    } 		 
    else
      image.src = file;
  }
}