In the continuation of a series on debugging web applications, the text delves into four fundamental debugging techniques: backtracking, reproduction, live instrumentation, and bisection. Backtracking involves retracing steps in the code to identify the source of an error, while reproduction focuses on methodically replicating the actions that led to a bug to better understand its cause. Live instrumentation provides real-time monitoring to uncover issues that might not appear during testing, using tools like Highlight, LogRocket, and Sentry to observe application behavior in production. Bisection helps pinpoint the exact commit where a bug was introduced by comparing different versions of the application, with "git bisect" offering an automated way to streamline this process. Despite the time-consuming nature of debugging, the process is crucial for identifying loopholes, understanding the root causes of bugs, and implementing preventative measures to maintain robust applications.