open a centered pop-up window, sending arguments url, title, width, height

scripts.js

/* 
usage > centerPop('http://mypage.com/','mypage','575','440');"
*/

function centerPop(url, title, w, h) {
    var dualScreenLeft = window.screenLeft != undefined ? window.screenLeft : screen.left;
    var dualScreenTop = window.screenTop != undefined ? window.screenTop : screen.top;

    var width = window.innerWidth ? window.innerWidth : document.documentElement.clientWidth ? document.documentElement.clientWidth : screen.width;
    var height = window.innerHeight ? window.innerHeight : document.documentElement.clientHeight ? document.documentElement.clientHeight : screen.height;

    var left = ((width / 2) - (w / 2)) + dualScreenLeft;
    var top = ((height / 2) - (h / 2)) + dualScreenTop;
    var newWindow = window.open(url, title, 'scrollbars=no, width=' + w + ', height=' + h + ', top=' + top + ', left=' + left);

    if (window.focus) {
        newWindow.focus();
    }
}