HTTP Errors in Web Hosting: What Do Error 403, 500, 502 & Co. Mean?

HTTP error codes provide clues as to why a website or service is not accessible. The following errors occur particularly frequently in web hosting.

403 – Forbidden

Meaning
Access to the requested resource is not allowed.

Common Causes

• Incorrect file or folder permissions (e.g. 777 or 000)

• Missing start file (index.php, index.html)

• Access blocked by security rules (firewall / ModSecurity)

• Access restrictions in the .htaccess

What You Can Do

• Check the file permissions:

  • Folders: 755

  • Files: 644

• Make sure a start file is present

• Temporarily disable security plugins or protection mechanisms for testing

• Check existing .htaccess rules

406 – Not Acceptable

Meaning
The request was rejected by the server due to security or content rules.

Common Causes

• ModSecurity blocks certain parameters or forms

• Suspicious characters in URLs or form fields

• Misconfigured plugins or themes

What You Can Do

• Remove special characters from URLs or forms

• Temporarily disable plugins or web application firewalls for testing

• Test the site without custom .htaccess rules

• Contact support and provide the affected URL

429 – Too Many Requests

Meaning
Too many requests have been sent to the server in a short period of time.

Common Causes

• Bots or crawlers accessing the website too frequently

• Misconfigured plugins (e.g. cronjobs or API requests)

• External services or scripts with high request frequency

What You Can Do

• Check and limit cronjobs or API access

• Enable caching (e.g. browser or server cache)

• Block suspicious IP addresses

• Reduce automatic background queries

500 – Internal Server Error

Meaning
The server cannot properly execute or interpret the application.
The exact cause is initially unknown.

Common Causes

• PHP error or incompatible PHP version

• Defective or faulty plugins/themes

• Insufficient PHP memory limit

What You Can Do

• First check the php_error.log
  (in the home directory under /log)

• Temporarily set the PHP version to an older/stable version for testing

• Temporarily rename the .htaccess file for testing

• Gradually deactivate plugins

502 – Bad Gateway

Meaning
The web server receives an invalid response from a connected service
(e.g. PHP-FPM).

Common Causes

• PHP process crashed or overloaded

• Script execution times too long

• Misconfiguration between web server and PHP

What You Can Do

• Reload the page (often a temporary problem)

• Reduce the complexity of plugins or scripts

• Increase PHP limits if necessary (memory / execution time)

• Check recently changed PHP settings

503 – Service Unavailable

Meaning
The server is currently unavailable. 

Common Causes

• Server overload

• Maintenance work

• Too many simultaneous processes

• Service restarts

What You Can Do

• Wait a few minutes and reload the page

• Check if updates or maintenance are in progress

• Reduce simultaneous accesses (e.g. through caching)

• Contact support if the error persists

504 – Gateway Timeout

Meaning
A connected service took too long to respond.

Common Causes

• Very slow database queries

• Unreachable external APIs

• Long script execution times or large data processing

What You Can Do

• Optimize plugins and database queries

• Temporarily disable external services for testing

• Reduce import or export processes

General Note

Many of these errors are configuration- or load-related and often occur after the following changes:

• Updates

• Plugin installations

• PHP version changes

• Traffic spikes

If an error is reproducible or persists for a longer period, support will be happy to help.
Please provide, if possible:

• the affected URL

• the time the error occurred

• a brief description of the last changes