Web applications that store state information are somewhat more complex than those that don't. Given these considerations, it's clearly best to avoid storing state.
Applications differ widely in their state storage requirements.
These traditional World Wide Web applications don't need to store state information. At the other extreme are commercial applications that let users wheel virtual shopping carts from page to page, selecting items for purchase. These applications must keep track of order information on a  per-user basis. Considering that a popular site could have scores of simultaneous sessions, these commercial applications must employ a sophisticated means of handling state for each session. Somewhere between these extremes are applications with simple state storage requirements, such as keeping track of the total number of votes on an  issue, the number of visitors to the web site, and so on.