Edit in JSFiddle

alpha.style.background = 'red';
beta.style.border = '5px dotted green';

var div = document.createElement('div');
div.id = 'gamma';
div.className = 'box';
document.body.appendChild( div );

gamma.style.background = 'blue';

<div id="alpha" class="box"></div>

<img src="http://www.mariowiki.com/images/9/90/BowserRoarSmallAni.gif" name="beta" class="box" />

.box {
    width: 100px;
    height: 100px;
    border: 1px solid;
    float: left;
    margin: 5px;
}