1. 簡書類

實現效果

html代碼

<div class="container">
    <form action="" class="parent">
        <input type="text" class="search" placeholder="搜索">
        <input type="button" name="" id="" class="btn">
    </form>
</div>

css代碼

* {
    margin: 0;
    padding: 0;
}
.container {
    height: 70px;
    width: 800px;
    margin: 100px auto 0 auto;
}
.parent {
    position: relative;
}
.search {
    width: 300px;
    height: 40px;
    border-radius: 18px;
    outline: none;
    border: 1px solid #ccc;
    padding-left: 20px;
    position: absolute;
}
.btn {
    height: 35px;
    width: 35px;
    position: absolute;
    background: url("images/topbar.png") no-repeat -2px -99px;
    top: 6px;
    left: 285px;
    border: none;
    outline: none;
    cursor: pointer;
}

2. 百度類

實現效果

html代碼

<div class="container">
    <form action="" class="parent">
        <input type="text">
        <input type="button" value="百度一下">
    </form>
</div>

css代碼

重點：
1.當input框foucus時，border顏色改變，而不是保留outline
2.button按鈕預設box-sizing: border-box

.container {
                width: 500px;
                height: 50px;
                margin: 100px auto;
            }
            
            .parent {
                width: 100%;
                height: 42px;
                top: 4px;
                position: relative;
            }
            
            .parent>input:first-of-type {
                /*輸入框高度設置為40px, border占據2px，總高度為42px*/
                width: 380px;
                height: 40px; 
                border: 1px solid #ccc;
                font-size: 16px;
                outline: none;
            }
            
            .parent>input:first-of-type:focus {
                border: 1px solid #317ef3;
                padding-left: 10px;
            }
            
            .parent>input:last-of-type {
                /*button按鈕border並不占據外圍大小，設置高度42px*/
                width: 100px;
                height: 44px; 
                position: absolute;
                background: #317ef3;
                border: 1px solid #317ef3;
                color: #fff;
                font-size: 16px;
                outline: none;
            }