You can also put a nice border around your elements. Try this:

<!-- ... -->
    div {
      color: white;
      background-color: green;
      width: 300px;
      height: 200px;
      font-family: sans-serif;
      border: 5px solid black;
  <div>I am a div with a border</div>

Now you assigned your div to have a black border that is 5px thick and solid. Let’s dissect the border property a little bit with a different border and a generic description:

border: 20px dashed #ff88aa;
border: <line-width> || <line-style> || <color>;

Here you see an even thicker border that has a different color, and is also dashed instead of `solid. The color is a good example for how many different types of values a lot of CSS properties accept. There are a lot more than would fit nicely on this page. Often, you’ll find yourself searching the web for the accepted input values, or looking them up in the CSS spec (check links in the Resources section). This color value is in HEX RGB notation (meaning, hexadecimal red green blue). It can be convenient to use a color picker tool (you can find them online or even use good ol’ MSPaint!) to find the color you want and then copy and paste the value from there.