I write my code on GitHub, download the code, and test it on Newgrounds, then I repeat. It can be a bit annoying switching tabs a lot on old devices, and most of my testing is testing small stuff like if the transition in CSS works and looks good. It takes a long time before everything starts looking good, and it has to scale well with different screens. Then I continue on the game, and then spend a long time tweaking the visuals. I do not make high quality games, so I can only guess it's gonna become a real pain when trying to make a decent game.
Guidodinho
And after 2013 web design has started to slowly go down-hill. No more borders around things or clear indications of whats click-able or not.
Especially image galleries. If you now want too see the oldest image in a large collection: you gotta scroll-down, let stuff load, scroll down some more, let more stuff load, etc, etc, etc. And if your device is shitty, the browser page will crash when halfway through.
No more options to start with the oldest, or some buttons on top&bottom to go to first or last pages.
Only old-school forums seemed to keep those, sadly.