One of the big problems with the internet as we know it is unwanted, annoying adverts. But this - sorry to say - is the price we must all pay in return for using websites for free.
Google, Facebook, Instagram, Twitter and other services are expensive to run and because they are free to use, they need to pay their bills in other ways, including showing ads. Indeed, the site you are reading now, for free, is largely paid for by ads.
No-one likes to think too hard about how much their online activity is being tracked, but the simple fact is that it is being tracked and the data is used to show you ads in the hope you'll spend some money.
Does Facebook know what I search for on Google?
No. But many websites use a so-called Facebook Pixel, which gathers data about you - such as your IP address and other things - and advertisers use this data to put relevant ads on your Facebook timeline.
So, the bottom line is that Facebook bascially knows what you look at online.
How do I stop personalised ads appearing on Facebook?
Recently Facebook updated its interface on desktop and mobile. And it also launched a new tool called 'Off-Facebook activity'.
Using this you can prevent this tracking from being turned into targeted ads. Make no mistake: this does not stop the tracking, but it will mean you don't see adverts for services and products you've looked at recently.
You'll see the same number of adverts, but they won't be personalised to you. You can also find out how to block ads with these best ad-blockers.
To turn off the setting, you can do it on mobile or on a laptop / desktop by going to Facebook and then to Settings.
In a web browser, click the down arrow at the top right, then click Settings & Privacy (above). On the next menu, click Settings.
Look for Your Facebook Information on the left, click it and then on Off-Facebook activity.
Click View (to the right) and you may be asked to re-enter your Facebook account password. Now click on Manage your off-Facebook activity.
Click the toggle button marked Future off-Facebook activity.
You'll see a message explaining what will happen and that it can take up to 48 hours to fully disconnect from your Facebook account, so you might see targeted adverts for a short while after changing the setting. Click the Turn Off button.
On a phone, it's much the same process. Tap the three horizonal lines at the top right, then scroll down until you see Settings & Privacy, then tap Settings.
Scroll down until you find Off-Facebook activity, and then turn off future activity.
Watch out for this Facebook scam.