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  // Кнопочга вверх
    $('.lift').click(function () {
        $('body,html').animate({
            scrollTop: 0
        }, 400);
        return false;
    });
    
    $(window).scroll(function(event) {if ($(window).scrollTop() >250) { $('.lift').show()} else {$('.lift').hide()};});

.lift {
  background: lightblue;
  height: 36px;
  width: 36px;
  text-align: center;
  color: #fff;
  position: fixed;
  left: 15px;
  bottom: 15px;
  line-height: 40px;
  font-size: 20px;
  cursor: pointer;
}