For the purpose of this demo, I'll use a StackOverflow element for credibility.

If you sign out of SO, you can see a large call to action box at the top of the page. Even easier, just go to their new Portuguese version here - <https://pt.stackoverflow.com/>

Once you see the call to action box (captured below) go ahead and inspect it with developer tools.

![enter image description here](https://i.stack.imgur.com/HqnOi.png)

On the div with the ID of `hero-content`, you will notice a style that I have pasted below:

```
#herobox #hero-content {
   background: #fff7d8;
   border: none;
}

```

I have done some research and as we all know, div ID's *should* be unique to the page. Although, if they are unique, why would a selector need to state an ID within an ID?