var DHTML = (document.getElementById || document.all || document.layers);

// get a named object on the page
// from http://www.quirksmode.org/js/cross_dhtml.html
function getObj(name) {
  if (document.getElementById) {
        this.obj = document.getElementById(name);
        this.style = document.getElementById(name).style;
  }
  else if (document.all) {
        this.obj = document.all[name];
        this.style = document.all[name].style;
  }
  else if (document.layers) {
        this.obj = document.layers[name];
        this.style = document.layers[name];
  }
}

// decide if an element exists on the page
function isValidObj(name) {
  if (document.getElementById) {
        return (document.getElementById(name)!=null);
  }
  else if (document.all) {
        return (document.all[name]!=null);
  }
  else if (document.layers) {
        return (document.layers[name]!=null);
  }
  return false;
}

var AgntUsr=navigator.userAgent.toLowerCase();
var Opr=AgntUsr.indexOf("opera")!=-1;
if (DHTML && Opr) {
  if (isValidObj('navbooksbtn')) {
    var navbooksbtn = new getObj('navbooksbtn');
    navbooksbtn.style.display="none";
    navbooksbtn.style.visibility="hidden";
  }
  else {
    alert('navbooksbtn not found');
  }
}