Final answer:
When adding custom critical validation rules, you can integrate them within the server-side code and implement client-side validation using JavaScript.
Step-by-step explanation:
When it comes to adding custom critical validation rules, it largely depends on the specific context. However, in the realm of web development, a common approach is to integrate the rules within the server-side code.
For instance, if you're using a server-side language like PHP, you can add custom critical validation rules directly within your server-side code. This allows you to control the validation process and ensure that the necessary checks are performed before accepting user input.
In addition to server-side validation, it's also advisable to implement client-side validation using JavaScript. This provides a seamless user experience by validating input in real-time before the data is sent to the server.