.css-yidnqd-InlineLink:link{color:#3F3F42;}.css-yidnqd-InlineLink:visited{color:#696969;}.css-yidnqd-InlineLink:link,.css-yidnqd-InlineLink:visited{font-weight:bolder;border-bottom:1px solid #BABABA;-webkit-text-decoration:none;text-decoration:none;}.css-yidnqd-InlineLink:link:hover,.css-yidnqd-InlineLink:visited:hover,.css-yidnqd-InlineLink:link:focus,.css-yidnqd-InlineLink:visited:focus{border-bottom-color:currentcolor;border-bottom-width:2px;color:#B80000;}@supports (text-underline-offset:0.25em){.css-yidnqd-InlineLink:link,.css-yidnqd-InlineLink:visited{border-bottom:none;-webkit-text-decoration:underline #BABABA;text-decoration:underline #BABABA;-webkit-text-decoration-thickness:1px;text-decoration-thickness:1px;-webkit-text-decoration-skip-ink:none;text-decoration-skip-ink:none;text-underline-offset:0.25em;}.css-yidnqd-InlineLink:link:hover,.css-yidnqd-InlineLink:visited:hover,.css-yidnqd-InlineLink:link:focus,.css-yidnqd-InlineLink:visited:focus{-webkit-text-decoration-color:currentcolor;text-decoration-color:currentcolor;-webkit-text-decoration-thickness:2px;text-decoration-thickness:2px;color:#B80000;}}A blog post from Dan Levy, vice-president of ads, suggested that Facebook needs it to be possible to track users’ activities across other apps and websites, in order to help its advertisers target their posts at those people who would most likely be responsive.

https://www.bbc.co.uk/news/technology-55339569