function scrollOffsetX() {
    return window.pageXOffset ?
                window.pageXOffset : document.documentElement.scrollLeft ?
                    document.documentElement.scrollLeft : document.body.scrollLeft;
}

function scrollOffsetY() {
    return window.pageYOffset ?
                window.pageYOffset : document.documentElement.scrollTop ?
                    document.documentElement.scrollTop : document.body.scrollTop;
}

function screenWidth() {
    return document.innerWidth ?
                document.innerWidth : document.documentElement.clientWidth ?
                    document.documentElement.clientWidth : document.body.clientWidth;
}

function screenHeight() {
    return document.innerHeight ?
                document.innerHeight : document.documentElement.clientHeight ?
                    document.documentElement.clientHeight : document.body.clientHeight;
}

function windowScrolling() {
    if ($("#__bike_details_popup").length > 0) {
        var popupX = (screenWidth() - $('#__bike_details_popup')[0].offsetWidth) / 2 + scrollOffsetX();
        var popupY = (screenHeight() - $('#__bike_details_popup')[0].offsetHeight) / 2 + scrollOffsetY();
        $("#__bike_details_popup").css(
            {
                "left": popupX + "px",
                "top": popupY + "px"
            }
        );
        $("#__bike_details_popup_frame").css(
            {
                  "left": popupX + 5 + "px",
                  "top": popupY + 5 + "px", 
                  "width": $('#__bike_details_popup')[0].offsetWidth - 20 + "px", 
                  "height": $('#__bike_details_popup')[0].offsetHeight - 20 + "px"
            }
        );
    }
    if ($("#__popup_shadow").length > 0) {
        var shadowX = (screenWidth() - $('#__popup_shadow')[0].offsetWidth) / 2 + scrollOffsetX();
        var shadowY = (screenHeight() - $('#__popup_shadow')[0].offsetHeight) / 2 + scrollOffsetY();
        $("#__popup_shadow").css(
            {
                "left": shadowX + "px",
                "top": shadowY + "px"
            }
        );
    }
}

window.onscroll = windowScrolling;
window.onresize = windowScrolling;