As a backend developer, ensuring that your code is secure is essential to protect against potential threats. In this article, we will explore some secure coding guidelines that web developers should follow to build secure web applications.

1. Input Validation: One of the most important things that developers can do to secure their web applications is to validate all user inputs. Input validation should be done on both client and server sides to prevent malicious inputs like SQL injection and cross-site scripting (XSS) attacks.
2. Sanitization: It's important to sanitize the user inputs as well, especially when dealing with form submissions. Sanitization can help remove unwanted and harmful characters and ensure that the data being submitted is in the expected format.
3. Authentication: Authentication is a critical aspect of web application security. Developers should ensure that they use strong password hashing mechanisms, limit the number of login attempts, and implement multi-factor authentication to increase security.
4. Authorization: Authorization is another key aspect of web application security. Developers should implement role-based access control to ensure that only authorized users can access specific resources and functions.
5. Secure Session Management: Session management is important in web applications. Developers should ensure that session IDs are encrypted and that they are refreshed periodically to prevent session hijacking.
6. SQL Injection Prevention: To prevent SQL injection attacks, developers should use parameterized queries, stored procedures, and prepared statements.
7. Cross-Site Scripting Prevention: To prevent cross-site scripting attacks, developers should use output encoding techniques like HTML entities and JavaScript escaping.
8. Secure Communication: Developers should use HTTPS for secure communication between the client and server to prevent man-in-the-middle attacks.
9. Error Handling: Error handling is important for web applications, but developers should ensure that they don't leak sensitive information in error messages that can be exploited by attackers.
10. Security Testing: Finally, developers should perform security testing on their web applications to identify and fix vulnerabilities before the application goes live.

In conclusion, following these secure coding guidelines can help web developers build secure web applications that are protected against potential security threats. Input validation, sanitization, authentication, authorization, secure session management, SQL injection prevention, cross-site scripting prevention, secure communication, error handling, and security testing are all essential aspects of web application security that developers should consider when building a web application. By following these guidelines, developers can ensure that their web applications are secure and reliable.