function pagelock(){
if (document.compatMode == 'CSS1Compat') {
        width  = document.documentElement.scrollWidth;
        height = document.documentElement.scrollHeight;
    } else {
        width  = document.body.scrollWidth;
        height = document.body.scrollHeight;
    }
document.getElementById("overlay_img").height = height;
document.getElementById("overlay_img").width = width;
}