Cookies accumulating on a home computer
Euro-MPs have voted to accept an amendment to a draft privacy bill that would block the placing of cookies on users' computers without their permission.
Critics of the proposal say the motion could make the net more troublesome to use and inconvenience many websites.
The draft directive will now go before the European Parliament for a second reading. Even if it is adopted, it will not come into effect for several years because individual nations must pass their own laws to enforce it.
Cutting cookies
The measure is part of a privacy bill aimed at increasing security when people are sending faxes and e-mails or using their mobile phone.
The bill would prohibit unsolicited commercial messages or spam to phones, faxes and possibly e-mail.
The amendment lets member states choose an "opt-in" or "opt-out" method of controlling spam.
The opt-out option prevents the sending of spam to people who have said they do not want to get it by putting their name on a national register.
The directive also blocks the placing of cookies on users' computers without their permission.
Cookies are small files that many of the websites you visit place on your machine. Different sites use them for different purposes. But essentially all of them act as identification devices.
Some cookies are a convenience because they remember registration details. This means that you don't have to sign in every time you return to that favourite site.
Some financial sites use cookies as an additional security check and to record what users are doing. Some sites demand that people accept cookies before they can use their services.
Other cookies are used to direct people to a particular subsection of a site that users previously expressed a preference for.
Cookie creator
Most controversial are the cookies that advertisers use to record which adverts users see. This helps them monitor the effectiveness of ad campaigns and work out who is seeing them.
Some browsers, such as Microsoft's Internet Explorer 6.0, let users refuse the third-party cookies installed by advertisers. Other browsers do not allow cookies to be created at all.
The Interactive Advertising Bureau (IAB) condemned the ban and said it would cause problems for many websites.
"Cookies form the fundamental transmission mechanic that powers the internet," said Danny Meadows-Klue, chairman of the IAB.
"A change in the law will restrict and frustrate people using the internet, forcing them to re-register or re-enter preferences every time they re-visit a site," he said.
The IAB claims that the move could cost British companies £187m as online adverts become less effective and advertisers re-think marketing strategies.
Now the directive has been accepted the IAB said it would lobby to have the amendment overturned before it gets a second reading before the parliament.