max-width: 100%;//父元素的宽度

display: block;

margin: 0 auto;

    display: table-cell; 垂直居中

    vertical-align: middle;

style="max-width: 100%;max-height: 100%; display:inline-block;"  //水平居中

  text-indent:50px; 段落首行缩进50个像素

    <style>

        ::-webkit-scrollbar { //隐藏滚动条

            display: none;

        }

    </style>

   <div style="width: 30%;display: inline-block;" class="code">

                            <div class="code-img" style="height: 34px;text-align: center;">

                                <img style=" display: inline-block;max-width: 100%;max-height: 100%;vertical-align: middle;"

                                    src="1.jpg" alt="" id="captchaImg">

                            </div>

                        </div>