$(document).ready( function(){
  $(".yt_thumb").click(function() {
		$('li.yt_thumb-active').removeClass('yt_thumb-active');
	  //$(this).removeClass("button"); 
	  $(this).addClass("yt_thumb-active"); 
  $(".yt_player").html(play($(this).find("a").attr("href")));
$("#video_content").html($('img', $(this)).attr("title"));
return false; 
  });
});