[html] How to make div's percentage width relative to parent div and not viewport

Here is the HTML I am working with.

<div id="outer" style="min-width: 2000px; min-height: 1000px; background: #3e3e3e;">_x000D_
  <div id="inner" style="left: 1%; top: 45px; width: 50%; height: auto; position: absolute; z-index: 1;">_x000D_
    <div style="background: #efffef; position: absolute; height: 400px; right: 0px; left: 0px;"></div>_x000D_
  </div>_x000D_
</div>

What I would like to happen is for the inner div to occupy 50% of the space given to its parent div(outer). Instead, is is getting 50% of the space available to the viewport, which means that as the browser/viewport shrinks in size, so does it.

Given that the outer div has min-width of 2000px, I would expect the inner div to be at least 1000px wide.

Use position: relative on the parent element.

Also note that had you not added any position attributes to any of the divs you wouldn't have seen this behavior. Juan explains further.