This is kind of a really nooby question, and I think I already know the answer, but:
Can you add Scrollbars to the side of a <div>?
div {
height: 100px;
overflow: auto;
}
You give an explicit height so the div doesn't expand to fit its content.
If you only want horizontal or vertical scrolling, use overflow-x and overflow-y respectively.
If down the track you want the extra content to be hidden, use overflow: hidden.
The default for overflow property is visible.