display_popup = function() {
    var w = document.getElementById('popup').offsetWidth;
    var d_width  = document.body.clientWidth;
    document.getElementById('trans').style.width = window.screen.width;
    document.getElementById('trans').style.height = window.screen.height;
    document.getElementById('popup').style.left = (d_width - w) / 2;
    document.getElementById('close').style.left = (d_width - w) / 2 + w;
};
close_popup = function() {
    document.getElementById('trans').style.display = 'none';
    document.getElementById('popup').style.display = 'none';
    document.getElementById('close').style.display = 'none';
};
window.onscroll = function()  {
    if (window.screen.height < document.body.clientHeight + document.body.scrollTop)
        document.getElementById('trans').style.height = document.body.clientHeight + document.body.scrollTop;
};