Going asleep last night, I rememberedd that I ought to make a mental note of where I had stopped watching a rather complex movie before I nodded off.  A mental bookmark, I thought.  Then I wondered how it was that a computer metaphor so suited what is a familiar cognitive operation, and one which presumably long pre-dates browser lists of favourites.  The answer is of course that bookmarks in browsers exist precisely because they support a familiar cognitive operation.  When we see a bookmark, we are looking at something which results from our cognitive economy.  Technology is a sketch of ourselves, adn getting better.  In affordance terms, the bookmark in the browser is pure affordance.  It serves no purpose and has no reality except in terms of what it affords us.  One more example of looking outwards to see our minds.