在<ul > 标签(带有CSS)中选择第二和第三个元素(Li)

ul > :first-child{
    margin-right: 50px;
}

ul > :first-child + li{
    margin-right: 50px;
}

ul > :first-child + li + li{
    margin-right: 50px;
}
li:nth-child(n+2):nth-child(-n+3) {
  margin-right: 50px;
}

这将同时选择第二个和第三个li

测试代码

<style>
    li:nth-child(2) {
        margin: 50px 0 0 100px;
        color: red;
    }
</style>

<body>
    <ul>
        <li>1</li>
        <li>2</li>
        <li>3</li>
        <li>4</li>
        <li>5</li>
        <li>6</li>
    </ul>
</body>




禁止右键

<script>
    document.oncontextmenu = function(){
        return false;
    }
</script>

<script>
    $(function(){
        $(document).contextmenu(function() {
            return false
        })
    });
</script>

禁止F12

<!DOCTYPE html><html><head>
    <meta charset="UTF-8">
    <title>js禁止f12事件</title>
    <script>
        window.onload = function(){
            document.onkeydown = function(event){
                var ev = event || window.event || arguments.callee.caller.arguments[0];
                //123 代表F12键
                if(event.keyCode = 123){
                    return false;
                }
            }
        }
    </script></head><body><p>这里是一些内容</p></body></html>