This is used to indicate [external links like this](https://developer.mozilla.org/en-US/).
```css
a[href*="//"]:not([href*="w.allsup.co"])::after {
  color: #888;
  vertical-align: super;
  font-size: 0.8em;
  content: "🡕";
}
```
More elaborate:
```css
a[href*="//"]:not([href*=".allsup.co/"]) {
  color: red;
}
a[href*="//"]:not([href*=".allsup.co/"]):after {
  content: "↑";
  font-size: 13px;
}
a[href*="//"][href*=".allsup.co/"] {
  color: orange;
}
a[href*="//"][href*=".allsup.co/"]:after {
  content: "→";
  font-size: 13px;
}
a[href]:not([href*="//"]) {
  color: green;
}
```