[Vlasenko Fedor]

<style>
#x {
  width: 200px;
  height: 200px;
  overflow: scroll;
  overflow-x: hidden;
  margin-top: 20px;
}

.control {
  position: fixed;
  top: 0;
  right: 0;
}

</style>
<div id="x">
  <a name="1"></a><b>text</b> text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text
  text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text
  text
  <a name="2"></a><b>text</b> text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text
  text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text
  text
  <a name="3"></a><b>text</b> text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text
  text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text
  text text text text text text text text text text text t
  <a name="4"></a><b>text</b> text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text text
  text text text text text text
</div>
<div class="control">
  <a id="prev" href="#">Назад</a>
  <a id="next" href="#">Вперед</a>
</div>
<script>
function nav(arr) {
  var current = 0,
    len = arr.length - 1;
  this.next = function() {
    current = current < len ? current + 1 : 0;
    return arr[current];
  };
  this.prev = function() {
    current = current > 0 ? current - 1 : len;
    return arr[current];
  };
}
var links = document.querySelectorAll('#x a[name]'),
  control = new nav(links),
  a = document.createElement('a');
prev.onclick = function() {
  a.href = '#' + control.prev().name;
  a.click();
  return false;
}
next.onclick = function() {
  a.href = '#' + control.next().name;
  a.click();
  return false;
}
</script>