To create a semi-transparent background, use the rgba function for setting the parent's background color with alpha transparency. For example:
.Container {
background-color:rgb(0,0,0); /* fallback for IE 8 and below */
background-color:rgba(0,0,0,0.5);
}
.Text {
color:rgb(255,255,255);
}
While this code adjusts the background opacity of the container, it does not affect the children elements. To change the children's opacity, you need to define another class with specific opacity values like this:
.OtherChildItem {
opacity:0.5;
filter:alpha(opacity=50); /* IE 8 and below */
}
If you prefer using a background image, adjust the opacity directly on the image itself (using a PNG format).