1. An article of manufacture having computer readable storage medium comprising computer readable program code executable by a computer to implement a method of detecting tasks, said medium comprising: computer readable program code labeling each URL in a set of URLs with a token; computer readable program code defining a task grammar based on identifying a plurality of tasks, each task based on a feasible sequence of tokens representing a sequence of URLs accessed to accomplish that task; computer readable program code receiving a web access log; computer readable program code extracting and tokenizing a sequence of accessed URLs from said web access log, said sequence of URLs part of said set of URLs for which said task grammar is defined; computer readable program code applying said task grammar to said tokenized sequence of accessed URLs; and computer readable program code, based on said applying said task grammar, identifying and reporting one or more tasks, each identified task comprising at least one of the following: a task that comprises one or more sub-tasks, a task that is carried over several sessions, a partial task in one session, and a group of tasks in one session.