inline-block <span>
get 100% width of parent if have multiple lines of text inside. Why first span get width of it content, but second get width of parent?
h1{text-align:center;}
span{border:1px solid #000; display:inline-block;}
<div style="width:500px;">
<h1><span>aaaaaaaa</span></h1>
<h1><span>aaaaaaaa aaaaaaaa aaaaaaaa aaaaaaaa aaaaaaaa</span></h1>
</div>