min-height does not work with body

First, declare a doctype so you're in standards if you haven't already.

Now, the body can only be as high as the containing html, so you need to set HTML tag to 100% height, and body to min-height 100%. This works for me on Firefox.

html {height:100%} 
body {min-height:100%}

This worked for chrome 64 without setting a hard-coded height:

html {
    min-height: 100%;
    display: flex;
}

body {
    flex: 1;
}