function bn_go_right()
{
  var tbl=document.getElementById("lenta");
  var bn=document.getElementById("bn");
  var left=tbl.style.left.substr(0,tbl.style.left.length-2);
  left=left.replace(/,/,'.')*1-bn.offsetWidth+5;
  if (left<(bn.offsetWidth-tbl.offsetWidth))
    left=bn.offsetWidth-tbl.offsetWidth;
  tbl.style.left=left+"px";
  bn_set_nav();
}
function bn_go_left()
{
  var tbl=document.getElementById("lenta");
  var bn=document.getElementById("bn");
  var left=tbl.style.left.substr(0,tbl.style.left.length-2);
  left=left.replace(/,/,'.')*1+bn.offsetWidth-5;
  if (left>5)
    left=5;
  tbl.style.left=left+"px";
  bn_set_nav();
}
function bn_set_nav()
{
  var tbl=document.getElementById("lenta");
  var bn=document.getElementById("bn");
  var left=tbl.style.left.substr(0,tbl.style.left.length-2);
  left=left.replace(/,/,'.')*1;
  if (left==bn.offsetWidth-tbl.offsetWidth)
    document.getElementById("rbutt").style.visibility="hidden";
  else
    document.getElementById("rbutt").style.visibility="visible";
  if (left==5)
    document.getElementById("lbutt").style.visibility="hidden";
  else
    document.getElementById("lbutt").style.visibility="visible";
}