This is a very nice idea, nicely presented too.

Bug report: There's a typo in the actual popup as shown to me, it says "extention". Consistently enough, the typo is present in the code snippet in the article:

    if (!document.cookie.includes("notice-shown")) {
        document.getElementById("ad-note-hidden").id = 'ad-note';
        document.getElementById("ad-note-content-wrapper").innerHTML = "No adblocker detected. " + 
        "Consider using an extention like <a href=https://ublockorigin.com/>uBlock Origin</a> to save time and bandwidth." +
        " <u onclick=hide()>Click here to close.</u>";
    }