You will need to install a user script manager extension to install this script.
For a list of features, see the comprehensive introduction to the script in the Flickr Hacks forum.
Flickr Fixr debuted here as a userscript back in 2015, but userscript-version ain't updated anymore and probably doesn't work properly. Instead you should install a version of the browser extension:
You might also want to try one of my other userscripts: