pop-under window before current page

JavaScript
function makePopunder(pUrl) {
var _parent = (top != self && typeof (top["document"]["location"].toString()) === "string") ? top : self;
var mypopunder = null;
var pName = (Math["floor"]((Math["random"]() * 1000) + 1));
var pWidth = window["innerWidth"];
var pHeight = window["innerHeight"];
var pPosX = window["screenX"];
var pPosY = window["screenY"];
var pWait = 3600;
pWait = (pWait * 1000);
var pCap = 50000;
var todayPops = 0;
var cookie = "_.mypopunder";
var browser = function () {
    var n = navigator["userAgent"]["toLowerCase"]();
    var b = {
        webkit: /webkit/ ["test"](n),
        mozilla: (/mozilla/ ["test"](n)) && (!/(compatible|webkit)/ ["test"](n)),
        chrome: /chrome/ ["test"](n),
        msie: (/msie/ ["test"](n)) && (!/opera/ ["test"](n)),
        firefox: /firefox/ ["test"](n),
        safari: (/safari/ ["test"](n) && !(/chrome/ ["test"](n))),
        opera: /opera/ ["test"](n)
    };
    b["version"] = (b["safari"]) ? (n["match"](/.+(?:ri)[\\/: ]([\\d.]+)/) || [])[1] : (n["match"](/.+(?:ox|me|ra|ie)[\\/: ]([\\d.]+)/) || [])[1];
    return b;
}();

function isCapped() {
    try {
        todayPops = Math["floor"](document["cookie"]["split"](cookie + "Cap=")[1]["split"](";")[0]);
    } catch (err) {};
    return (pCap <= todayPops || document["cookie"]["indexOf"](cookie + "=") !== -1);
};

function doPopunder(pUrl, pName, pWidth, pHeight, pPosX, pPosY) {
    if (isCapped()) {
        return;
    };
    var sOptions = "toolbar=no,scrollbars=yes,location=yes,statusbar=yes,menubar=no,resizable=1,width=" + pWidth.toString() + ",height=" + pHeight.toString() + ",screenX=" + pPosX + ",screenY=" + pPosY;
    document["onclick"] = function (e) {
        if (isCapped() || window["pop_clicked"] == 1 || pop_isRightButtonClicked(e)) {
            //return;
        };
        window["pop_clicked"] = 1;
        mypopunder = _parent["window"]["open"](pUrl, pName, sOptions);
        if (mypopunder) {
            var now = new Date();
            document["cookie"] = cookie + "=1;expires=" + new Date(now["setTime"](now["getTime"]() + pWait))["toGMTString"]() + ";path=/";
            now = new Date();
            document["cookie"] = cookie + "Cap=" + (todayPops + 1) + ";expires=" + new Date(now["setTime"](now["getTime"]() + (84600 * 1000)))["toGMTString"]() + ";path=/";
            pop2under();
        };
    };
};

function pop2under() {
    try {
        mypopunder["blur"]();
        mypopunder["opener"]["window"]["focus"]();
        window["self"]["window"]["blur"]();
        window["focus"]();
        if (browser["firefox"]) {
            openCloseWindow();
        };
        if (browser["webkit"]) {
            openCloseTab();
        };
    } catch (e) {};
};

function openCloseWindow() {
    var ghost = window["open"]("about:blank");
    ghost["focus"]();
    ghost["close"]();
};

function openCloseTab() {
    var ghost = document["createElement"]("a");
    ghost["href"] = "about:blank";
    ghost["target"] = "PopHelper";
    document["getElementsByTagName"]("body")[0]["appendChild"](ghost);
    ghost["parentNode"]["removeChild"](ghost);
    var clk = document["createEvent"]("MouseEvents");
    clk["initMouseEvent"]("click", true, true, window, 0, 0, 0, 0, 0, true, false, false, true, 0, null);
    ghost["dispatchEvent"](clk);
    window["open"]("about:blank", "PopHelper")["close"]();
};

function pop_isRightButtonClicked(e) {
    var rightclick = false;
    e = e || window["event"];
    if (e["which"]) {
        rightclick = (e["which"] == 3);
    } else {
        if (e["button"]) {
            rightclick = (e["button"] == 2);
        };
    };
    return rightclick;
};
if (isCapped()) {
    return;
} else {
    doPopunder(pUrl, pName, pWidth, pHeight, pPosX, pPosY);
};

Source

Also in JavaScript: