The ePrivacy directive – more specifically Article 5(3) – requires prior informed consent for storage or for access to information stored on a user's terminal equipment. In other words, you must ask users if they agree to most cookies and similar technologies (e.g. web beacons, Flash cookies, etc.) before the site starts to use them. (27) The exact moment of the completion of the transmission of a communication, after which traffic data should be erased except for billing purposes, may depend on the type of electronic communications service that is provided. For instance for a voice telephony call the transmission will be completed as soon as either of the users terminates the connection. For electronic mail the transmission is completed as soon as the addressee collects the message, typically from the server of his service provider. (28) The obligation to erase traffic data or to make such data anonymous when it is no longer needed for the purpose of the transmission of a communication does not conflict with such procedures on the Internet as the caching in the domain name system of IP addresses or the caching of IP addresses to physical address bindings or the use of log-in information to control the right of access to networks or services. (29) The service provider may process traffic data relating to subscribers and users where necessary in individual cases in order to detect technical failure or errors in the transmission of communications. Traffic data necessary for billing purposes may also be processed by the provider in order to detect and stop fraud consisting of unpaid use of the electronic communications service. http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:32002L0058:EN:HTML