Sometimes websites do not appear in the browser as we expect. Images do not show up, or formatting seems to be broken or nonexistent.
This issue can occur due to a myriad of reasons but often is caused by Apache or PHP errors that should be investigated by the website developer.
To get a bigger picture, here are a few things you can do.
1. Browser Console
You'll want to review the Network and Console tabs for errors. These interfaces may show you different scripting errors, missing files (404 status) or other status codes that are concerning (500, 503)
2. Tail the Apache and PHP logs.
You can tail the Apache error log while refreshing the web page with the following command run as root:
tail -n0 -f /var/log/apache2/error_log
Please note that this log may show errors specific to your site. Still, it may also be busy with other Apache related messages or related to different websites depending on how many websites are on the server.
To find the PHP error log, it may be in the file named error_log in the website's document root, or in /home/user/logs as indicated in Why is my PHP website blank.