Web elements unexpectedly highlighted when I click on them in browsers, disappears after a few seconds

Hello. As a new macOS user i would like to ask a question. When im clicking on something while im on browser there is a pink highlited box that appears at that time and disappears after 2 seconds. It always appears when i click on something specifically on browsers. i got an image showing that box. Is there any option to stop that? Thanks in advance!

[Re-Titled by Moderator]