css transparent background image

1/* Use RGBA */
2background-color: rgba(255, 255, 0, 0.75); /* Transparent Yellow */

1#bg{
2background-image: url('images/wood1.jpg');
3opacity:0.2;
4width:300px;
5height:300px;
6}
7

1background: linear-gradient(rgba(0,0,0,0.5), rgba(0, 0, 0, 0.5)), url(image.jpg) 

1.opacity30 {
2  opacity: 0.3;
3  filter: alpha(opacity=30); /* For IE8 and earlier */
4}

1background-color: rgba(255, 0, 0, 0.5);

1.selector {
2  background-image: url(image.png);
3}