AdBlockers are web browser plugins, extension or addon that block advert such as Google Adsense found an any website such as AdBlock plus. Most internet users have this plugin activated and that number is in the increase.
If you as a site owner, your main source of income is from displaying Ads of various Ad-network on your website, this can be frustrating because there is a drastic deep in revenue generation.
Dealing With Adblock
Most website prefer to do nothing in dealing with AdBlock menace, others politely ask users to whitelist them while some completely hide it content or redirect users to given page on detection of AdBlock.
Add this script on your sites index after </head> tag