Safari has been stalling when I load some websites. Github.com is the most reproducible. The page would load, but then my mouse would turn to a beach-ball and just get stuck until I close the tab with Github or whatever site seems to be causing it.
I am not running any extensions - to be honest I don't know what it could be. My boss is having the same issue as well. I have no issues with loading Github on Chrome.
I am running macOS Sierra (10.12.1) on a Late 2014 Mac mini and Safari 10.0.1. It also happens on the Safari Technology Preview (Release 26, 10.2)
What are ways to fix this or further diagnose slow web sites in safari?