It is generally recommended to use external stylesheets for styling HTML elements. However, there are a few reasons why inline CSS maybe used is certain situations.

• Quick Styling: When you need to apply a quick, one-time style to a specific element on a single page, using inline CSS can be more convenient than creating a separate stylesheet.
• Specific Overrides: Inline styles can be used to override external or internal stylesheet rules for a specific element. This is useful when you want to make a targeted change to a particular element.
• Dynamic Styling: In some dynamic web applications, styles may need to be applied dynamically based on calculated server-side conditions. Inline styles can be generated and applied programmatically in those scenarios.
• Email Templates: In email templates, inline styles are often used to ensure consistent rendering where external stylesheets cannot be applied.
• Embedded Styles in HTML Emails: Some HTML emails include inline styles to ensure that the email content is displayed correctly across different email clients, as external stylesheets are often not supported.
• Specificity Requirements: Inline styles have high specificity, which means they can override styles defined in external stylesheets or internal styles. This can be useful when dealing with complex styles and specificity conflicts.

While inline CSS has its use cases, external stylesheets promote better organization, reusability, and easier maintenance of styles across multiple pages. The choice between inline and external styles depends on the specific needs and context of the project.

It is also recommended that external JavaScripts are used wherever feasible. However, Inline JavaScript, like inline CSS, is used in certain situations for specific purposes. Here are some scenarios where inline JavaScript might be employed:

• Quick Actions: Similar to inline CSS, inline JavaScript can be used for quick, one-time actions on a specific element on a page. For simple event handling, including JavaScript directly in the HTML can be more straightforward and easier to use.
• Event Handling: If you want to attach a specific behavior or action to an HTML element, you can use inline JavaScript to handle events directly. For example, you might use the onclick attribute to define a JavaScript function that executes when a button is clicked.
• Dynamic Content: Inline JavaScript can be used to generate or manipulate content dynamically on the client side. This is often done when the content needs to be modified based on user interactions or dynamic conditions.
• HTML Templating: In some cases, inline JavaScript may be used for simple HTML templating to dynamically generate HTML content.
• Specific Overrides: Inline JavaScript can be used to override behavior defined in external scripts. This might be necessary in certain scenarios, although it's generally recommended to organize code in a way that avoids the need for such overrides.

While inline JavaScript can serve above scenarios, it is often recommended to use external JavaScript files. External scripts provide better code organization, reusability, and ease of maintenance. Additionally, separating HTML, CSS, and JavaScript into distinct files helps to keep code clean and promotes a better separation of concerns.