Forum software solutions have a way of indicating whether threads (and in the case of Daniweb forums to) have had their content viewed by a user.
How exactly is this done? Is reference to every page a user has explored stored somewhere, for every user (or for every page)? That seems like a huge amount of data potentially..
A solution I figured out was to write the modified date of a target file to a query string variable when rendering hyperlinks to that file; in most browsers, this makes links show as visited when a user has seen the target file but only if the target file hasn't been modified since the last time they saw it.
This is by no means ideal because a user might come on from a different computer or browser; and could think that they haven't followed any links...
I'm all for implementing detailed tracking per-authenticated user; but that means only authenticated users get the benefit of knowing when things are 'new'. Still; I suppose I could create a new guest account for every IP address.
Is there something I'm missing? I can see myself blowing my storage allowance on per-page user tracking O_o