<script type="text/javascript">     
  function op(obj){     
  if(document.getElementById){     
  var el = document.getElementById(obj).style.display = "block";     
  var ar = document.getElementById("masterdiv").getElementsByTagName("div");     
  for (var i=0; i<ar.length; i++) { if (ar[i].className=="minfa") ar[i].style.display = "none";}     
  }     
  }     
  </script>     
  <a href="javascript://" onClick="op(i1); return false;">Оснавная инфа</a> <a href="javascript://" onClick="op(i2); return false;">Дополнительная инфа</a>     
  <div id="masterdiv">     
  <div id="i1" class="minfa">$BRIEF$</div>     
  <div id="i2" style="display:none" class="minfa">$MESSAGE$</div>     
  </div>