DIV#mysterycontainer {
	background-color: blue;
	height: 50px;
	width: 50px;
	position: absolute;
    margin-top: 10px;
    margin-left: auto;
    margin-right: auto;
}

#mysterynumber {
    /* the inner div centers the content vertically & horizontally */
    position: absolute;
    top: 50%;
    height: 1em;
    margin-top: -0.5em;
    width: 100%;
    vertical-align: middle;
    text-align: center;

	color: silver;
	font-size: xx-large;
}