Question: I can’t get `padding-bottom` to work when I use `overflow-y: auto` on a box. I use Firefox.

```css
#container {
  padding: 3em;
  overflow-x: hidden;
  overflow-y: auto;
  width: 300px;
  height: 300px;
  background: red;
}

#some_info {
  height: 900px;
  background: #000;
}
```

```html
<div id="container">
  <div id="some_info"></div>
</div>
```

See the [JSFiddle](https://jsfiddle.net/rwgZu/).

Answer: 
The solutions above were not working for my needs, and I think I stumbled on a simple solution.

If your container and overflowing content share the same background color, you can **add a top and bottom border with the color matching the background color**. To create equal padding all around, set the border width equal to the left and right padding of the container.

Link to modified version of OP's fiddle: <http://jsfiddle.net/dennisoneil/rwgZu/508/>

A simple example below.

**Note**: Stack Overflow puts the snippet results *into an overflow scroll*, which makes it a little harder to see what's going on. The fiddle may be your best preview option.

```css
#container {
  background: #ccc;
  overflow-y: scroll;
  height: 190px;
  padding: 0 20px;
  border-top: 20px solid #ccc;
  border-bottom: 20px solid #ccc;
}
#overflowing {
  background: #ccc;
}
```

```html
<div id="container">
  <div id="overflowing">
    This is content<br/>
    This is content<br/>
    This is content<br/>
    This is content<br/>
    This is content<br/>
    This is content<br/>
    This is content<br/>
    This is content<br/>
    This is content<br/>
    This is content<br/>
    This is content<br/>
    This is content<br/>
    This is content<br/>
    This is content<br/>
    This is content<br/>    
  </div>
</div>
```
I think `@-moz-document url-prefix()` is what you need.

```css
#container {
    padding: 3em;
    overflow-x: hidden;
    overflow-y: auto;
    width: 300px;
    height: 300px;
    background: red;
}

#some_info {
    height: 900px;
    background: #000;
}

@-moz-document url-prefix() {
  #container > :last-child {
    margin-bottom: 3em;
  }
}
```

```html
<div id="container">
  <div id="some_info"></div>
</div>
```