Many folks use adblock solutions when visiting sites. There is nothing wrong with that. But ad-blockers do impact how much money bloggers and publishers make. BlockAlyzer Adblock Counter is a handy plugin that lets you know how many of your visitors actually use an ad blocker.
BlockAlyzer shows you how badly you are being affected by ad blockers. You will see unique visitors, share of AdBlock users, the number of page views your site is getting. You do have the option to compare your data against others but sharing is voluntary. The plugin is available for free.