Many of us use ad blockers these days. While there is nothing wrong with that, many of our favorite websites rely mainly on ads to stay afloat. If you have the same problem on your own site, you can use plugins like AdSense Unblocker to aggressively target AdBlock users.
This plugin simply blocks AdBlock users from viewing your site. You will be able to show a custom message to your visitors to encourage them to support your website. Webmasters have the option to modify the appearance of their message from the back-end.
Whether you should block AdBlock users from viewing your site is up for debate. This free plugin lets you test the idea though.