1. Introduction

This tutorial aims to guide you through implementing secure coding practices in web development. By the end of this tutorial, you'll understand how to write secure code that reduces security vulnerabilities.

You will learn:
- The importance of secure coding
- How to identify common security flaws
- Techniques and practices to write secure code

Prerequisites:
- Basic knowledge of web development (HTML, CSS, JavaScript)
- Familiarity with a backend language (such as PHP, Python, Node.js)

2. Step-by-Step Guide

Understanding Secure Coding

Secure coding is the practice of writing code that is immune from the common security vulnerabilities. It includes understanding the vulnerabilities, their consequences, and techniques to avoid them.

Common Security Flaws

Some of the common security flaws are:
- Injection attacks (such as SQL, OS, and LDAP injection)
- Cross-Site Scripting (XSS)
- Cross-Site Request Forgery (CSRF)
- Insecure Direct Object References
- Unvalidated Redirects and Forwards

Secure Coding Techniques

To avoid these security flaws, follow these techniques:
- Always validate user inputs: Never trust user input, always validate and sanitize it.
- Use parameterized queries: It can help you prevent SQL injection.
- Encode data: Encoding the data can help you prevent XSS attacks.
- Use secure cookies: Set secure and HttpOnly flags for cookies.
- Use HTTPS: Always use HTTPS instead of HTTP to protect the data in transit.

3. Code Examples

Example 1: Input Validation

// Bad practice
let user = req.body.user;

// Good practice
let user = sanitizeInput(req.body.user);

In the bad practice example, the user input is directly used without any validation or sanitization. In the good practice example, the input is sanitized before use.

Example 2: Parameterized Queries

# Bad practice
query = f"SELECT * FROM users WHERE name = '{user_input}'"

# Good practice
query = "SELECT * FROM users WHERE name = %s"
params = [user_input]

In the bad practice example, the user input is directly used in the query which can lead to SQL injection. In the good practice example, a parameterized query is used.

4. Summary

We have learned about secure coding, common security flaws, and techniques to avoid them. The next step would be to delve deeper into each of these security vulnerabilities, understand them in detail, and learn more about how to prevent them. Here are some additional resources:
- OWASP Top 10
- Google's Web Security Academy

5. Practice Exercises

1. Exercise 1: Write a function to validate and sanitize user inputs.
2. Exercise 2: Convert the following SQL query into a parameterized query: SELECT * FROM users WHERE name = user_input
3. Exercise 3: Write a function to set secure and HttpOnly flags for cookies.

Solutions:

// Solution 1
function sanitizeInput(input) {
  return input.replace(/<|>/g, "");
}

// Solution 2
let query = "SELECT * FROM users WHERE name = ?";
let params = [user_input];

// Solution 3
res.cookie('session', '1', { secure: true, httpOnly: true });

Tips for Further Practice: Check out the OWASP Cheat Sheet Series for more in-depth knowledge and exercises on secure coding practices.