Выпадающее горизонтальное меню с поиском на CSS3 и HTML5

<ul class="nav">
    <li id="settings">
        <a href="#"><img src="images/settings.png"></a>
    </li>
    <li>
        <a href="#">Приложения</a>
    </li>
    <li>
        <a href="#">Сервис</a>
    </li>
    <li id="search">
        <form action="" method="get">
            <input name="search_text" id="search_text" placeholder="Поиск..." type="text">
            <input name="search_button" id="search_button" type="button">
        </form>
    </li>
    <li id="options">
        <a href="#">Меню</a>
        <ul class="subnav">
            <li><a href="#">Настройки</a></li>
            <li><a href="#">Приложения</a></li>
            <li><a href="#">Сервис</a></li>
            <li><a href="#">Разное</a></li>
        </ul>
    </li>
</ul>

* {
    margin: 0; 
    padding: 0;
}

.nav {
    background: #232323;
    height: 60px;
    display: inline-block;
}
 
.nav li {
    float: left;
    list-style-type: none;
    position: relative;
}

.nav li a {
    font-size: 16px; 
    color: white;
    display: block;
    line-height: 60px;
    padding: 0 26px;
    text-decoration: none;
    border-left: 1px solid #2e2e2e;
    font-family: sans-serif, Arial;
    text-shadow: 0 0 1px rgba(255, 255, 255, 0.5);
}
.nav li a:hover {
    background-color: #2e2e2e;
}
 
#settings a {
    padding: 18px;
    height: 24px;
    font-size: 10px;
    line-height: 24px;
}

#search {
    width: 357px;
    margin: 4px;
}
#search_text {
    width: 297px;
    padding: 15px 0 15px 20px;
    font-size: 16px;
    font-family: sans-serif, Arial;
    border: 0 none;
    height: 52px;
    margin-right: 0;
    color: white;
    outline: none;
    background: #1f7f5c;
    float: left;
    box-sizing: border-box;
    transition: all 0.15s;
}
::-webkit-input-placeholder { /* WebKit браузеры */
    color: white;
}
:-moz-placeholder { /* Mozilla Firefox 4 to 18 */
    color: white;
}
::-moz-placeholder { /* Mozilla Firefox 19+ */
    color: white;
}
:-ms-input-placeholder { /* Internet Explorer 10+ */
    color: white;
}
#search_text:focus {
    background: rgb(64, 151, 119);
}
#search_button {
    border: 0 none;
    background: #1f7f5c url("../images/search.png") center no-repeat;
    width: 60px;
    float: left;
    padding: 0;
    text-align: center;
    height: 52px;
    cursor: pointer;
}

#options a {
    border-left: 0 none;
}
#options>a {
    background-image: url("../images/triangle.png");
    background-position: 85% center;
    background-repeat: no-repeat;
    padding-right: 42px;
}
.subnav {
    visibility: hidden;
    position: absolute;
    top: 110%;
    right: 0;
    width: 200px;
    height: auto;
    opacity: 0;
    transition: all 0.1s;
    background: #232323;
}
.subnav li {
    float: none;
}
.subnav li a {
    border-bottom: 1px solid #2e2e2e;
}
#options:hover .subnav {
    visibility: visible;
    top: 100%;
    opacity: 1;
}