Session cookies are temporarily stored on the user's computer purely for technical and functional purposes. These cookies allow for the transmission of the necessary session identifiers in order to ensure safe and efficient browsing on the website; they are deleted at the end of the “session” (hence the name), when the browser is closed. By using this type of cookie, other computer techniques that are potentially detrimental to users' privacy when browsing can be avoided.
Persistent cookies remain stored on the computer's hard drive until their expiration date or deletion by the user/visitor. Persistent cookies allow any visitor (or any other user who uses the same computer) to be automatically recognized when they log on to the site. Many user-friendly features are provided through persistent cookies (for example, browser language preferences can be saved, or items can be stored in a shopping cart while making purchases online). Nevertheless, persistent cookies can also be used to deliver advertising to the user, and may even be used purposes of dubious legality. Users can set their browsers to accept/reject all cookies, or to prompt them each time a cookie is offered so that they can decide whether to accept it or not. In any case, users are able to change their default settings and disable cookies (that is, definitively block them) by setting their browsers to the highest level of protection.