nav {
    margin: 0 auto;
    width: 1250px;
    min-width: 1250px;
    display: -webkit-flex;
    display: flex;
}

.dropdownmenu ul {
    list-style: none;
    width: 100%;
}

.dropdownmenu li {
    float: left;
    position: relative;
    width: auto;
}

.dropdownmenu a {
    background-color: #005ca2; /*#30A6E6;*/
    /*color: #005ca2;*/
    display: block;
    font-size: 18px;
    font-family: "HYZHONGYUANJ";
    text-align: center;
    text-decoration: none;
    height: 50px;
    line-height: 50px;
    -webkit-transition: all .25s ease;
    -moz-transition: all .25s ease;
    -ms-transition: all .25s ease;
    -o-transition: all .25s ease;
    transition: all .25s ease;
}

.dropdownmenu img {
    margin: 0 auto;
    width: 24px;
    vertical-align: middle;
}

.dropdownmenu li:hover a {
    background: #ff6600;
}

#submenu {
    left: 0;
    opacity: 0;
    position: absolute;
    top: 50px;
    visibility: hidden;
    z-index: 1;
}

li:hover ul#submenu {
    opacity: 1;
    top: 50px; /* adjust this as per top nav padding top & bottom comes */
    visibility: visible;
}

#submenu li {
    float: none;
    width: 100%;
    border-bottom: 1px solid #d8d8d8;
}

#submenu a:hover {
    background: #fff;
    color: #ff6600;
}

#submenu a {
    background-color: #ecf8ff;
    color: #005ca2;
}