how to add transparent background in css code example

Example 1: css how to make background transparent

/* Use RGBA */
background-color: rgba(255, 255, 0, 0.75); /* Transparent Yellow */

Example 2: css opacity example

.opacity30 {
  opacity: 0.3;
  filter: alpha(opacity=30); /* For IE8 and earlier */
}

Example 3: transparent background css for image

background-color: rgba(255, 0, 0, 0.5);

Example 4: image opacity in html

img {
  opacity: 0.5;
}