[рони]

Samsam,

<style type="text/css">
.ta{
    max-height:100px;
  }
  </style>
  <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
<meta charset="utf-8">
<script>
  jQuery(function($) {
    var min = 100;
    $(".ta").each(function(indx, el) {
        var b = $(el),
            max = el.scrollHeight,
            a = b.next(".read-next");
        if (max <= 100) a.hide();
        else a.on("click", function(event) {
            var h = b.height();
            b.css({'max-height' : (h < max ? max : min)+'px'});
            $(this).text(h < max ? "Svernut" : "OPen all");
            return false
        })
    })
});
</script>

  <div style="height:100%">
    <div class="ta" style="overflow:hidden">
   text<br>text<br>text<br>texttexttexttext<br>text<br>text<br>texttexttext<br>text<br>text<br>texttext<br>text<br>text<br>
    </div><a class="read-next" href="#">OPen all</a>
  </div>