Charlie recently had a rant about newsreaders who don’t understand what it means to ‘log on’. I couldn’t agree with him more. I think the minimum requirements for logging onto something are supplying a user name and a password, and I write for a computer magazine so I should know.
Still, it’s not always that straightforward: technology moves pretty quickly and sometimes it leaves the English language struggling to keep up, or at least to form a consensus.
One area I find particularly problematic is when referring to online sources. If you’re reporting a quote from somebody’s blog, for example, are they writing in it, on it or at it?
We use ‘in it’, which seems to best reflect the role of a blog as a journal or notebook, but what about websites in general? Clearly you ‘visit’ or ‘go to’ one rather than logging on (unless it’s your bank), but is information published on it, by it, at it, in it or to it?
I’d argue that this one is much less clear-cut. You might see some illuminating things on a website that have been published by it. You could perhaps say that they’re available at it, at a push.
Publishing to a website doesn’t sound right though; surely the site itself is the medium through which you publish to the readership? You don’t publish to a magazine, you publish in a magazine. But not in a website.
I suppose it must be the same with any new communication channel. I wonder if, when the grapevine was first invented, there was similar confusion about whether you heard things through or on it?
Thinking about it, I expect it came as something of a surprise either way.

Could we draw any distinctions based on the structure of the site itself? For example, the home page or top level of the web site could be the surface, so “on” is used. Once you get to a lower level, it becomes “in”.
In this context, “at” might well be usable for any addenda to a specific created object. you would post “on” the front page of a blog, and leave a comment “at” that post.
I’d stress that all of this is dependent on the actions undertaken. Where rules already exist they should be used, and in many cases a precise use of language should help matters.
If it helps…
Information is published *on* a website. It is published *at* a URL/URI. This is not redundant and can’t be conflated; one is an object, the other is a reference in an assumed address space. They normally covary, but consider such things as rebranding and mirror sites to see how anomalies might arise.