Plenty of webmasters are taking an aggressive approach to dealing with people who use ad blockers on their website. Some go as far as removing access to their site unless ad blockers are disabled. Ad Blocking Advisor for WordPress lets you take a gentler approach. It displays a notification bar to your visitors who are using an ad blocker, encouraging them to whitelist your site.
You have the option to allow your visitors to remove the banner at any time. This plugin is available as a free download.