f(window.location.hash){
            var el = document.getElementById(decodeURIComponent(window.location.hash.substr(1)));
            if(el) markElement(el);
        }
    }

    var registerXrefLink = function(link){
        var el = document.getElementById(decodeURIComponent(link.getAttribute("href").substr(1)));
        if(el){
            link.addEventListener("click", function(){
                markElement(el);
            });
        }
    }

    var registerXrefLinks = function(root){
        root 