What are the initial troubleshooting steps for a 'localhost/phpmyadmin HTTP Error 404'?

The first steps involve verifying that your web server (e.g., Apache, Nginx) is running correctly. Check its status through your XAMPP, WAMP, MAMP, or direct service management interface. Also, confirm the exact URL you are using in your browser. A common mistake is a typo in 'phpmyadmin' or incorrect case sensitivity depending on your operating system and web server configuration. Ensure that there are no other services hogging port 80 (or 443 if using HTTPS), which would prevent your web server from starting.