Web parameter such as "tab=6". The tab represents a particular view of information. It would be better IMO to give the view names, such as "view=detail", "view=summary", etc. The name should not be tied to tab positition, and perhaps not the tab name either if the name does not represent the kind of view in any meaningful way.
I've done that kind of thing before when the customer couldn't make up their flippin' mind what to call something and I couldn't think of a reliable generic description.