how to write text in middle of straight line in css

1h2 {
2   width: 100%; 
3   text-align: center; 
4   border-bottom: 1px solid #000; 
5   line-height: 0.1em;
6   margin: 10px 0 20px; 
7} 
8
9h2 span { 
10    background:#fff; 
11    padding:0 10px; 
12}