自动隐藏成省略号和显示

<abbr title="People's Republic of China">PRC</abbr> was founded in 1949.
<p title="Free Web tutorials">W3School.com.cn</p>

<style type="text/css">
        .alter {
        width: 100px;
        overflow:hidden; 
        display:block;
        white-space:nowrap;
        text-overflow:ellipsis;

    }