Two web browser extensions that prevent cookie notifications on websites have been developed within this thesis. The motivation for developing the extensions is the new European legislation that requires website administrators to equip their sites with visible notifications that cookies are used within the website. The user's preferences of accepting or rejecting website cookies can be recalled by the developed extensions. On any subsequent visit to a website last user's action about accepting website notices is automatically carried out. The process of developing extensions for Google Chrome and Mozilla Firefox web browsers, as well as a description of different development techniques and approaches are presented in the thesis. A demonstration of publishing both extensions in the official web browsers' web stores is also shown in the thesis.