Fixed position but relative to container

Question

I am trying to fix a div so it always sticks to the top of the screen, using:

position: fixed;
top: 0px;
right: 0px;

However,

Answer 1

2019 SOLUTION: You can use position: sticky property.

Here is an example CODEPEN demonstrating the usage and also how it differs from position: fixed.

How it behaves is explained below:

1. An element with sticky position is positioned based on the user's scroll position. It basically acts like position: relative until an element is scrolled beyond a specific offset, in which case it turns into position: fixed. When it is scrolled back it gets back to its previous (relative) position.

2. It effects the flow of other elements in the page ie occupies a specific space on the page(just like position: relative).

3. If it is defined inside some container, it is positioned with respect to that container. If the container has some overflow(scroll), depending on the scroll offset it turns into position:fixed.

So if you want to achieve the fixed functionality but inside a container, use sticky.