.highlight_textarea {
    height: 100px;
    border: 1px solid #ccc;

    /*给div添加可以调整控制盒子大小的属性*/
    resize: both;
    overflow: auto;
    outline: none;
}
 /* 输入框为空时显示 placeholder */
 .highlight_textarea:empty:before {
    content: attr(placeholder);
 }
 /* 输入框获取焦点时移除 placeholder */
 .highlight_textarea:focus:before {
    content: none;
}