SOURCE

<div class="search">
    <input type="search" class="inp">
    <a href="#" class="btn">搜索</a>
</div>

.search {
    height: 40px;
    width: 400px;
    margin: 0 auto;
    border: 2px solid #f3711c;
}
.search .inp {
    float: left;
    width: calc(80% - .1px);
    height: calc(100% - .1px);
    line-height: 40px;
    padding: 0;
    padding-left: 1em;
    border: none;
    outline: none;
    font-size: 16px;
}
.search .btn {
    float: right;
    width: 20%;
    line-height: 40px;
    text-align: center;
    vertical-align: middle;
    background: #f3711c;
    color: #fff;
    text-decoration: none;
}
.search .btn:hover {
    background: #ff5100;
}