function switch_page(from, to) {
    var el_from = document.getElementById(from);
    var el_to = document.getElementById(to);
    el_from.className = el_from.className.replace(new RegExp('(^|\\s)' + 'active-tab-body' + '(?:\\s|$)'), '$1');
    if (el_to.className != '') {
        el_to.className = el_to.className + ' active-tab-body';
    } else {
        el_to.className = 'active-tab-body';
    }
    
    var a_from = document.getElementById('linkexpress-shop.html#'+from);
    var a_to = document.getElementById('linkexpress-shop.html#'+to);
    a_from.className = a_from.className.replace(new RegExp('(^|\\s)' + 'active-tab' + '(?:\\s|$)'), '$1');
    if (a_to.className != '') {
        a_to.className = a_to.className + ' active-tab';
    } else {
        a_to.className = 'active-tab';
    }
}