Indeed. They were small images (https://old.reddit.com/r/nostalgia/comments/iv8hgg/the_netsc...) at the bottom of webpages linking you to netscape.com/microsoft.com so you could download the browser “recommended” (or targeted) by the page creator. These icons were usually a standard size (88x31 px?).
Wikipedia explains the context in whoch these were born a bit more: https://en.m.wikipedia.org/wiki/Browser_wars