Edit in JSFiddle

<div id="outer">
    
    <div id="inner">
        <div>!</div><p>this is any element of any width</p>
    </div>
    
</div>

/*-- for show only -- */
#outer {
    border: 1px solid black;
}

#inner {
    border: 1px dotted red;
}

/*-- all you actually need -- */

#outer {
    text-align: center;
}

#inner {
    display: inline-block;
}