The Pop-Under
windows and alerts 1999 deadOpen the ad, shove it behind the window, and let the visitor discover it after you are long gone.
In 2026: Dead twice over. Popup blockers kill the open call unless it comes from a click, and even when one is allowed, blur and focus no longer reorder windows, so the ad lands on top like an honest popup. The whole genre of deniable advertising rested on two lines browsers now ignore.
Where it came from: Perfected by the ad networks around 1999, litigated over for a decade afterwards. Wikipedia ↗
<script language="JavaScript">
// The pop-UNDER: open an ad, then immediately hide it behind yourself.
// The visitor finds it hours later, long after they can blame you.
var ad = window.open("sponsor.html", "ad",
"width=400,height=300,left=50,top=50");
if (ad) {
ad.blur(); // push the ad away
window.focus(); // pull yourself back on top
document.write("<p>Ad opened and buried.</p>");
} else {
document.write("<p>The browser refused to open it at all.</p>");
}
</script>