FACEBOOK users are being warned that the presents they purchase for loved ones ahead of Christmas may be revealed to them by accident.

Users who search for the perfect gift online could be targetted by “tracker ads” which will spoil the surprise when a family member or pal uses the same computer.

Rhys Gregory, digital director at Effective Communication, has explained how to avoid this happening at Christmas.

He told Wales Online: “Over the years online marketing has become very clever, which in most part can be beneficial to both the user and the organisation behind the website.

“As a user, you don’t want to see irrelevant ads for products or services that you’ll never buy.

“Likewise, a website that may be getting paid in return for you clicking on ads will only want to show you ads that you are more likely to click on.

“Whilst your actual identity will be kept anonymised in most situations, your device and your behaviour (the websites that you visit) won’t be.

“Cross-website tracking cookies allows the websites that you’re visiting to access this information.

“Which is why you may see an advert for a camera on Facebook, after you viewed photography equipment on Amazon.

“Usually you may be happy to see this, especially as it’s relevant to what you were looking at. But not if that camera was a gift for someone.”

How to prevent it occuring:

• When visiting a website for the first time, block all cookies or – if the website allows it – turn off marketing-related cookies.
• If you are returning to a website that you have already visited, go to the settings section of your internet browser. Select the Privacy option and opt to block all cookies, and also prevent cross-site tracking