<style>
    #list {
        width:200px;
    }
    #left {
        float:left;
        border:1px solid blue;
    }
    #right {
        float:right;
        word-break: break-all;
        word-wrap: break-word;
        /* 
        有一前提不能写死width属性
        因为像#block那块的#right宽度很明显与上面的不一致了
        */
        
        border:1px solid red;
    }
    #block {
        margin-left:60px;
    }
    .c {
        clear:both;
    }
    </style>
    <div id="list">
        <div>
            <div id="left">aaa</div>
            <div id="right">dddddddddddddddddddddddddddd</div>
            <div class="c"></div>
        </div>

        <div id="block">
            <div id="left">aaa</div>
            <div id="right">dddddddddddddddddddddddddddd</div>
            <div class="c"></div>
        </div>
    </div>