[teebrz]

Is it ethical to get up and get a cup of coffee on the clock? Stop and chat with coworkers? Browse the Internet?

It's unreasonable for employers to expect you to spend 100% of your time 100% focused on the 'task at hand'. You need to have a little downtime on the clock for reflection, thinking, stress relief, etc especially if you are a programmer. Frankly if I was an employer I'd be happy if you were using it try and keep sharp as opposed to looking at lolcats or something (not that there's anything wrong with that).

Of course this has to be "within reason", and an employer is well within their rights to decide that certain activities are too disruptive and ban them. Violating an explicit ban would be somewhat unethical.

Another question: is it a polite thing to do? There are certain general and company specific social norms for what and how much of that stuff is acceptable.

So I would say go for it, with the caveat that you shouldn't abuse the privilege.

This is for employees ofc. As a freelancer I try to be very conscientious about stopping the clock when I feel I'm not adding enough value for the client. I get paid a higher rate than I probably would otherwise, and therefore don't screw around. I do sometimes bill for reading that's done for research for the project, just as I don't stop the clock every time I look up something in the docs - but I do this as little as possible and always with the clients understanding.