Detecting Ad Blockers on Your Website

gistfile1.html

<div class="afs_ads">&nbsp;</div>
<script>
(function() {
    var message = "We've detected that you have an ad blocker enabled! Please enable it and help support our work!";

        // Define a function for showing the message.
        // Set a timeout of 2 seconds to give adblocker
        // a chance to do its thing
        var tryMessage = function() {
            setTimeout(function() {
                if(!document.getElementsByClassName) return;
                var ads = document.getElementsByClassName('afs_ads'),
                    ad  = ads[ads.length - 1];

                if(!ad
                    || ad.innerHTML.length == 0
                    || ad.clientHeight === 0) {
                    alert(message);
                    //window.location.href = '[URL of the donate page. Remove the two slashes at the start of thsi line to enable.]';
                } else {
                    ad.style.display = 'none';
                }

            }, 2000);
        }

        /* Attach a listener for page load ... then show the message */
        if(window.addEventListener) {
            window.addEventListener('load', tryMessage, false);
        } else {
            window.attachEvent('onload', tryMessage); //IE
        }
})();
</script>