I have some questions regarding the following css that I found:

html, body {
    height:100%;
    min-width:100%;
    position:absolute;
}

html {
    background: none repeat scroll 0 0 #fff;
    color:#fff;
    font-family:arial,helvetica,sans-serif;
    font-size:15px;
}

1. is it necessary to have height and min-width to 100% on the html and body? What's the benefit?
2. what is the reason for using position absolute?
3. why did they set the background/color/font on the html and not the body? Is there a difference? Or is it just preference?