Adblock Plus (ABP) is a free and open-source browser extension for content-filtering and ad blocking. It is developed by developer Wladimir Palant's Eyeo GmbH, a German software company. The extension has been released for Mozilla Firefox (including mobile), Google Chrome, Internet Explorer, Microsoft Edge (Chromium based version), Opera, Safari, Yandex Browser, and Android. In 2011, Adblock Plus and Eyeo attracted considerable controversy over its "Acceptable Ads" program to "allow certain non-intrusive ads" (such as Google Ads) to be allowed under the extension's default settings. While participation in the whitelisting process was free for small websites, large advertising companies were required to pay a fee in order for their ads to be whitelisted. Background The original version of Adblock (0.1) was written as a side project for Firefox by Danish software developer Henrik Aasted Sørensen, a university student at the time, in 2002. It hid image ads through user-defined filters from the page but did not actually prevent them from being downloaded. Sørensen maintained the open source project until Adblock 0.3 after which the project changed hands. This was also the last stable release of Adblock. Starting with Adblock 0.4, in early 2003, the development of Adblock was taken over by a developer who went by the pseudonym rue online. This version used XBL to hide the ads and with this objects like Flash or Java could also be blocked. But as with the original version the ads were still able to be downloaded. This was a developer build and not a stable release as were subsequent further versions (either released as nightly or development builds) making Adblock 0.3 the last stable release. Adblock 0.5, 2004, used content policies for ad blocking which prevented the ads from being downloaded instead of simply hiding them. Background images, scripts and stylesheets could be blocked through this approach as well. XBL support was dropped in this version in favor of content policies. These updates were implemented by rue with the help of Wladimir Palant who contributed other developments as well. Sometime after Adblock 0.5's release the development of the project stalled. Development stagnated beginning in 2004 and entirely stopped in early 2005. That's when Michael McDonald created a separate enhanced version of Adblock called Adblock Plus 0.5 to improve upon the original and add additional features. No update for the original Adblock was issued even after Firefox 1.5's release in November 2005. An official