To add a background image in CSS, you use the background-image property and specify the image URL inside the url() function. Here is the basic syntax:

css

selector {
  background-image: url('path_to_your_image.jpg');
}

Steps and tips:

• The path_to_your_image.jpg can be a relative path (e.g., "images/bg.jpg") or an absolute URL.
• By default, the image will repeat to fill the element. To prevent repetition, use background-repeat: no-repeat;.
• You can position the background image using background-position, for example, background-position: center center; to center it.
• To make the background image cover the entire element, use background-size: cover;.
• To keep the background fixed when scrolling, use background-attachment: fixed;.
• Always set a fallback background color with background-color in case the image fails to load.

Example:

css

body {
  background-image: url('background.jpg');
  background-repeat: no-repeat;
  background-position: center center;
  background-size: cover;
  background-attachment: fixed;
  background-color: #cccccc; /* fallback color */
}

This will add a centered, non-repeating background image that covers the entire viewport and stays fixed during scrolling

. You can also add multiple background images by separating URLs with commas:

css

body {
  background-image: url('image1.png'), url('image2.png');
  background-position: center, top;
  background-repeat: no-repeat, repeat;
}

The first image is closest to the viewer, and the last one is furthest

. In summary, adding a background image in CSS involves using the background- image property with the image URL, and optionally controlling repeat, position, size, and attachment for the desired effect.