British companies have 12 months to adopt an EU directive that affects what information they can store about visitors to their website.
The new laws on cookies, portions of information stored in your browser whenever you visit a website, come into effect on Thursday as part of the EU Privacy and Electronic Communications Directive.
The new rules mean that, in theory, websites must ask the users permission every time it wishes to access that personal information or log-in details.
The rules officially come into play across the European Union on Thursday, but it is thought that only two countries are fully implementing them with immediate effect.
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House in order
Information commissioner Christopher Graham says that a gradual approach gives British websites a year to abide by the new directive.
He said: "We're giving businesses and organisations up to one year to get their house in order.
"This does not let everyone off the hook. Those who choose to do nothing will have their lack of action taken into account when we begin formal enforcement of the rules."
There has been some opposition to the new privacy rulings, with retailers believing that constant pop-ups requesting permission from browsers could see British shoppers jump ship to American sites.