Why doesn't the height of a container element increase if it contains floated elements?

Question

I would like to ask how height and float work. I have an outer div and an inner div that has content in it. Its height may vary depending on the content of the inner div but

Answer 1

Its because of the float of the div. Add overflow: hidden on the outside element.

<div style="overflow:hidden; margin:0 auto;width: 960px; min-height: 100px; background-color:orange;">
    <div style="width:500px; height:200px; background-color:black; float:right">
    </div>
</div>

Demo