In our daily HTML design,  it is an easy job to horizontally center align an element with known width.<div class="element">I am<a href="http://www.aiubug.com" target="_blank" rel="external" title=""> bug </a>！</div>  .element{width:960px;margin:0 auto;}  The above codes set the width of the div block and horizontally center align it. It's very easy to implement. However, if we have some elements we don;t know their width and we still want to center align them. What should we do? The above code is not useful if we don't know the width before we center...