This may sound like a newbie question but I've searched all over and couldn't find a thing. I'm starting to think it isn't possible to do so? Maybe someone here will come along and prove me wrong.
Easier than that. Just go to the site, and click the favicon (the little icon to the left of the URL in the address bar)
and drag it to the right side of the dock (or the bottom, if you have the dock on the sides of your screen). Make sure you drop it between icons (they should move apart to make a space) rather than on one.
Easier than that. Just go to the site, and click the favicon (the little icon to the left of the URL in the address bar) View attachment 189052 and drag it to the right side of the dock (or the bottom, if you have the dock on the sides of your screen). Make sure you drop it between icons (they should move apart to make a space) rather than on one.