Until version 12, the Opera web browser had a menu with a big list of CSS override styles that worked like Firefox's Reader View. Some were for page development

Until version 12, the Opera web browser had a menu with a big list of CSS override styles that worked like Firefox's Reader View. Some were for page development/debugging, some emulated small screen devices, and a lot were there to improve readability. I have good vision and used the Opera CSS overrides and still use Firefox Reader View frequently because many web pages are poorly accessible even for people without disabilities. When Opera went to the WebKit rendering engine the CSS overrides were removed. I still miss them.