The blue arrow (marked in the figure above) hijacks the UP and DOWN in the keyboard and causes the page to jump on each result instead of scrolling smoothly. This page says that it has been bundled with Google Instant, and thus can be disabled ONLY by changing the search settings, which is inconvenient for private browsing.
Effected browsers: Chrome & Firefox; Edge is not effected (probably will be later)
Effected Websites: Google Search (Web, Image, Video, books, etc.)
OS: Windows 10, 64-bit.
The arrow keys are quick to use when you are on a laptop. And I lose what line I was reading when the page is jumping on each result, contrary to the smooth scrolling.
EDIT: It seems Google itself backed and scrapped this 'feature'. Arrows are now back to normal scrolling.