When working with CSS, some properties are fundamental to both structure and design. Three of the most important ones are color, margin, and font-family. The color property sets the text color, which directly affects readability and visual impact. For example, using h1 { color: darkblue; } makes headings stand out clearly on the page. The margin property controls the space outside an element. This spacing prevents content from appearing cluttered and enhances the overall layout. For instance, p { margin: 20px; } gives breathing room between paragraphs. Lastly, font-family sets the typeface for text, which contributes to the site's tone and personality. Using something like body { font-family: Arial, sans-serif; } ensures consistency across devices and keeps the content easy to read. Beyond these common properties, there are unique ones that add creative functionality. One example is box-shadow, which applies shadow effects to elements. For instance, box-shadow: 2px 2px 10px gray; adds subtle depth to a card or container, helping it stand out visually. Another unique property is transform, which allows elements to rotate, scale, or move. A popular use case is transform: scale(1.2); on hover to make icons or buttons more interactive. Lastly, clip-path lets you create non-rectangular shapes like circles or polygons. For example, clip-path: circle(50%); can turn a square image into a circular profile picture. These properties give you more control over how elements appear and behave, allowing for a more engaging user experience.