$(function(){
   setInterval(aleFunc, 100);
   var gmarkGray = $('#gray');
   var gmarkBlack = $('#black');
   
   function aleFunc(){
      var index = $('ul#js_slideNav li.on').index();
	  var idoCaption = $('#imagealt p');
	  
	  
	  idoCaption.empty();
	  idoCaption.append($('ul#main_img li img').eq(index).attr('alt'));
	  
	  if(index< 8){
	     $('#imagealt').css('color','#000')
	  } else { 
	     $('#imagealt').css('color','#fff')
	  };
	  
	  gmarkGray.hide();
	   gmarkBlack.hide();
	   if(index== 7){
	      gmarkBlack.show()
	  } else if((index == 10) || (index == 13)) {
	      gmarkGray.show()
	  };
	  
	  

	
	};
   
 });