On on and on at

A correspondent writes to ask if he can say both 'Open your book on page...' and 'Open your book at page...' Is there a difference?Prepositions can reflect personal perspective, if a situation allows it. A book is such a situation. It's both a physical object and a collection of content. Traditionally, the 'at' usage offers us the physical perspective. I left my bookmark at page 60.How far have you read? I'm at page 60.It's the usual use of 'at' to refer to location. The 'on' usage reflects content: He makes an interesting point on page 60.You'll find the answer on page 60.People are more likely to refer to the content of a book than to its physical character, so we would expect 'on' to be more common.'Opening a book' is an interesting example of overlap between the two perspectives. In one way it's a reference to location - so, 'at'. Most people would open a book 'at' a particular page. But people have a semantic reason for asking someone to open a book at a particular point - so 'on' isn't ruled out. In the first case, they're thinking 'where'; in the second, they're thinking 'what'.But I say, 'traditionally'. While I don't sense any change of usage in 'on' to refer to location, I do sense a change in 'at' with reference to content: The footnote is at page 60 - instead of traditional 'on'You'll find this at Chapter 3 - instead of traditional 'in'Here are some examples from Google:I found the answer at page 8.The earliest written account is at page 833 of...The section dealing with... Darwin's views is at page ...You'll find the answer at section 5...Why? I think it's the influence of the Internet, which has foregrounded the use of 'at' in fresh ways thanks chiefly to the use of @ and hash. The collocation of 'find', 'at', and 'page' is routine there, and is now being increasingly used offline. There are several other contexts in which prepositional usage is overlapping on the Internet. I've just used one. 'On' the Internet? Type 'find people on the Internet' into Google and you get some 3 million hits. Type 'find people in the Internet; and you get 6 million. You'll find this post 'on my blog'? 'in my blog'? 'at my blog'? Usage doesn't seem to have settled down yet.