About deploy a Codeigniter Web in Azure

You need to change your base URL in application/config.php. That's why your CSS aren't loading.

You got this at the moment.

Code:

<link rel="stylesheet" href="https://xpbc-app-2018.azurewebsites.net/xpbc2017/template/assets/plugins/bootstrap/css/bootstrap.min.css">
<link rel="stylesheet" href="https://xpbc-app-2018.azurewebsites.net/xpbc2017/template/assets/plugins/font-awesome/css/font-awesome.min.css">
<link rel="stylesheet" href="https://xpbc-app-2018.azurewebsites.net/xpbc2017/template/assets/fonts/style.css">
...

You are appending xpbc2017 for some reason.

Regarding 404 you need to enable the debug log in application/config.php and look for errors in /application/logs/. You can try to change to your default controller into w/e your login controller are named. So you know that's it your default controllers fault or not.