function previewComment(obj){
        url = $(obj).parent().attr('action');
        $.post(url,{data: $('form.send_comment textarea').val(), preview: "true"} ,function(data){
		data = eval('('+data+')');
		if(data.error == true){
			showMessage(data.msg);
		} else {
			if($('#comment_preview').length){
				$('#comment_preview').replaceWith(data.msg);
			} else {
				$('#last_comment').parent().after(data.msg);
			}
		}
	})
	return false;		
}