function toggle(div_id) {
        var el = document.getElementById(div_id);
        if ( el.style.display == 'none' ) {        el.style.display = 'block';}
        else {el.style.display = 'none';}
}
function blanket_size(popUpDivVar) {
        if (typeof window.innerWidth != 'undefined') {
                viewportheight = window.innerHeight;
        } else {
                viewportheight = document.documentElement.clientHeight;
        }
        if ((viewportheight > document.body.parentNode.scrollHeight) && (viewportheight > document.body.parentNode.clientHeight)) {
                blanket_height = 600;
        } else {
                if (document.body.parentNode.clientHeight > document.body.parentNode.scrollHeight) {
                        blanket_height = document.body.parentNode.clientHeight;
                } else {
                        blanket_height = document.body.parentNode.scrollHeight;
                }
        }
        var blanket = document.getElementById('blanket');
        blanket.style.height = blanket_height + 'px';
        var popUpDiv = document.getElementById(popUpDivVar);
        popUpDiv_height=800/4-150;//150 is half popup's height
        popUpDiv.style.top = popUpDiv_height + 'px';
}
function window_pos(popUpDivVar) {
        if (typeof window.innerWidth != 'undefined') {
                viewportwidth = window.innerHeight;
        } else {
                viewportwidth = document.documentElement.clientHeight;
        }
        if ((viewportwidth > document.body.parentNode.scrollWidth) && (viewportwidth > document.body.parentNode.clientWidth)) {
                window_width = viewportwidth;
        } else {
                if (document.body.parentNode.clientWidth > document.body.parentNode.scrollWidth) {
                        window_width = document.body.parentNode.clientWidth;
                } else {
                        window_width = document.body.parentNode.scrollWidth;
                }
        }
        var popUpDiv = document.getElementById(popUpDivVar);
        window_width=window_width/4-150;//150 is half popup's width
        popUpDiv.style.left = window_width + 'px';
}
function popup(windowname) {
        blanket_size(windowname);
        window_pos(windowname);
        toggle('blanket');
        toggle(windowname);
}