last_tab = 'tab1';

function show(layerName) {
    var shuffletop = document.getElementById(layerName);
    shuffletop.className = 'shuffletop';
}

function hide(layerName) {
    var shufflebot = document.getElementById(layerName);
    shufflebot.className = 'shufflebottom';
}

function show_next(tab_name) {
    document.getElementById(last_tab).className = 'tab';
    var curr = document.getElementById(tab_name);
    curr.className = 'tab_hover';
    hide(last_tab + '_data');
    show(tab_name + '_data');
    last_tab = tab_name;
}

function backToTop() {
    var x1 = x2 = x3 = 0; var y1 = y2 = y3 = 0;
    
    if (document.documentElement) {
        x1 = document.documentElement.scrollLeft || 0;
        y1 = document.documentElement.scrollTop || 0;
    }

    if (document.body) {
        x2 = document.body.scrollLeft || 0;
        y2 = document.body.scrollTop || 0;
    }

    x3 = window.scrollX || 0;
    y3 = window.scrollY || 0;
    var x = Math.max(x1, Math.max(x2, x3));
    var y = Math.max(y1, Math.max(y2, y3));
    window.scrollTo(Math.floor(x / 2), Math.floor(y / 2));

    if (x > 0 || y > 0) {
        window.setTimeout("backToTop()", 25);
    }
}