In what situations is it appropriate to use CSS for web page styling?

CSS is advisable for styling web pages in the following situations:

• When you need to separate the structure (HTML) from the appearance to facilitate support and scaling of the site.
• For setting styles of elements: colors, fonts, margins, layout, and animations.
• When creating responsive design so that the page displays correctly on different devices.
• To improve performance: styles are loaded once and applied to all pages.
• To ensure a consistent look of the site.

For example, instead of specifying color and font for each heading in HTML, you can define a style in CSS:

h1 {
  color: #333;
  font-family: Arial, sans-serif;
}

This simplifies work and makes the code cleaner and easier to modify.