background colour opacity html code example

Example 1: background color semi transparent

.transparent {
    background-color: rgba(255, 255, 255, 0.5);
}
.transparent {
    opacity: 0.5;
}

Example 2: css opacity example

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