解决方法
我想这就是你要找的东西：
http://jsfiddle.net/9BTYQ/1/
span {
color: white;
background-color: #343132;
Box-shadow: 0.5em 0 0 #343132,-0.5em 0 0 #343132;
}
div {
width: 100px;
}
<div>
<span>Do you have an idea to add a background-color property on a multi-line text,with two difficulties:</span>
</div>
