Wow, you all are so good! I have been posting from work for years. I sit at a computer all day and sometimes there's only so long you can stare at a spreadsheet, format a report, or sort through emails before you need a bit of a mental break. I will usually browse for 5-10 minutes at a time, then go back to my work for a couple hours. I work at a very large institution and no websites are blocked. I'm sure they have some way to keep track of where I've gone, but to my knowledge no one has ever looked into it or cares. I think supervisors have to jump through hoops to be given access to that information. Basically, I'd have to be looking at some pretty awful stuff before anyone noticed or cared. I know of one person who, years ago, was caught looking at porn on a work computer. And he wasn't fired, he works in a different department now.
Do I feel guilty about browsing this place? Not really. I'm on salary, I don't take breaks, I usually take a shortened lunch, and I work very hard when I am working. I'm much more productive when I can indulge in little internet breaks every now and then.