DigitalOcean is an un-managed provider so our team does not have direct access to the configuration files and logs within your droplet. While both our support team and the community here are happy to help you will need to provide a bit more information:

• What type of site is this? Static, PHP, another language...
• Are there any details recorded in your error log? For apache on Ubuntu this would be in /var/log/apache2/error.log
• Does restarting your web server resolve the issue?