html - How do I give text or an image a transparent background using CSS?

Is it possible, using CSS only, to make the background of an element semi-transparent but have the content (text & images) of the element opaque?

I'd like to accomplish this without having the text and the background as two separate elements.

When trying:

p {
  position: absolute;
  background-color: green;
  filter: alpha(opacity=60);
  opacity: 0.6;
}

span {
  color: white;
  filter: alpha(opacity=100);

  opacity: 1;
}

  Hello world

It looks like child elements are subjected to the opacity of their parents, so opacity:1 is relative to the opacity:0.6 of the parent.

Answer

Either use a semi-transparent PNG image or use CSS 3:

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

Here's an article from css3.info, Opacity, RGBA and compromise (2007-06-03).

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  Hello, World!