This is a bit older, but worthwhile. Rob Verger explains what most people do not understand about browsing the interwebs.
Your browser has a fingerprint. It’s not as obvious as the real ones on your fingertips, but it exists nonetheless. And advertising networks can use it to track your browsing.
Those Facebook and website like buttons have built-in trackers which follow you from website to website, and each visit gives advertisers ever more information about you.
If you want to take a step now to make your online browsing a little less trackable, consider installing a tool called Privacy Badger, also made by the Electronic Frontier Foundation.
Neat little tool but doesn’t work in Safari (Firefox, Chrome, Opera).