body{
    width: 500px;
}
pre {
    display: block;
    font-family: monospace;
    white-space: pre;
    margin: 1em 0;
    font-size: 16px;
    border:2px solid Black;
}

pre {
	overflow: auto;
	width: 450px;
	}

pre:hover {
	position: relative;
	width: 500px;
	z-index: 99;
	}