ul {
    /* 取消ul預設的內縮及樣式 */
    margin: 0;
    padding: 0;
    list-style: none;
}

    ul.drop-down-menu {
        border: #ccc 1px solid;
        display: inline-block;
        font-family: 'Open Sans', Arial, sans-serif;
        font-size: 13px;
    }

        ul.drop-down-menu li {
            position: relative;
            white-space: nowrap;
            border-right: #ccc 1px solid;
        }

        ul.drop-down-menu > li:last-child {
            border-right: none;
        }

        ul.drop-down-menu > li {
            float: left;
            /* 只有第一層是靠左對齊*/
        }

        ul.drop-down-menu a {
            background-color: #fff;
            color: #333;
            display: block;
            padding: 0 30px;
            text-decoration: none;
            line-height: 40px;
        }

            ul.drop-down-menu a:hover {
                /* 滑鼠滑入按鈕變色*/
                background-color: #ef5c28;
                color: #fff;
            }

        ul.drop-down-menu li:hover > a {
            /* 滑鼠移入次選單上層按鈕保持變色*/
            background-color: #ef5c28;
            color: #fff;
        }

        ul.drop-down-menu ul {
            border: #ccc 1px solid;
            position: absolute;
            z-index: 99;
            left: -1px;
            top: 100%;
            min-width: 180px;
        }

            ul.drop-down-menu ul li {
                border-bottom: #ccc 1px solid;
            }

                ul.drop-down-menu ul li:last-child {
                    border-bottom: none;
                }

            ul.drop-down-menu ul ul {
                /*第三層以後的選單出現位置與第二層不同*/
                z-index: 999;
                top: 10px;
                left: 90%;
            }

        ul.drop-down-menu ul {
            /*隱藏次選單*/
            display: none;
        }

        ul.drop-down-menu li:hover > ul {
            /* 滑鼠滑入展開次選單*/
            display: block;
        }