css3实现 依次出现三个点（一般用于提示加载中。。。 提交中。。。）

<a href="javascript:" class="login">登录中<span class="dotting"></span></a>

 .dotting { display: inline-block; width: 10px; min-height: 2px;
            padding-right: 2px;
            border-left: 2px solid currentColor; border-right: 2px solid currentColor;
            background-color: currentColor; background-clip: content-box;
            box-sizing: border-box;
            -webkit-animation: dot 1.5s infinite step-start both;
            animation: dot 1.5s infinite step-start both;
            *zoom: expression(this.innerHTML = '...');  /*IE7 */
        }
        .dotting:before { content: '...'; } /* IE8 */
        .dotting::before { content: ''; }
        :root .dotting { margin-left: 2px; padding-left: 2px; } /* IE9+ */

        @-o-keyframes dot {
            25% { border-color: transparent; background-color: transparent; }
            50% { border-right-color: transparent; background-color: transparent; }
            75% { border-right-color: transparent; }
        }
        @-ms-keyframes dot {
            25% { border-color: transparent; background-color: transparent; }
            50% { border-right-color: transparent; background-color: transparent; }
            75% { border-right-color: transparent; }
        }
        @-moz-keyframes dot {
            25% { border-color: transparent; background-color: transparent; }
            50% { border-right-color: transparent; background-color: transparent; }
            75% { border-right-color: transparent; }
        }
        @-webkit-keyframes dot {
            25% { border-color: transparent; background-color: transparent; }
            50% { border-right-color: transparent; background-color: transparent; }
            75% { border-right-color: transparent; }
        }
        @keyframes dot {
            25% { border-color: transparent; background-color: transparent; }
            50% { border-right-color: transparent; background-color: transparent; }
            75% { border-right-color: transparent; }
        }