Take web application offline in ASP.net MVC

While making changes or updating a web application we require to show a page that tells the end-user that the web application is under maintenance and won't be available for a while. To accomplish this requirement we add an Html page to the root directory of the web application named "App_offline.htm". 

This mainly helps us to show the end-user a user-friendly message instead of an ugly and flimsy error.  

Below is a code snippet of the contents for an "App_offline.htm" which is made using Bootstrap 3

<!doctype html>
    <title>Down for maintenance</title>
    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.4.1/css/bootstrap.min.css">
        .error-template {
            padding: 40px 15px;
            text-align: center;
            margin-top: 50px;

        .error-actions {
            margin-top: 15px;
            margin-bottom: 15px;

            .error-actions .btn {
                margin-right: 10px;
<body marginwidth="0" marginheight="0">
    <div class="container">
        <div class="row">
            <div class="col-md-12">
                <div class="error-template">
                        This site is currently down for maintenance
                    <div class="error-details">
                        We will be back up and running as fast as possible. <br /> Sorry for the inconvenience.

Download "App_offline.htm"