Question: I have a div tag contain text:

```
<div id="XXX" class="xxx">
    fffsdssfdf
</div>

```

And the CSS like this:

```
.xxx{
opacity :50;
}

```

But the Text doesn't opacity.

Answer: 
Opacity is a CSS 3 propery. It's expressed from 0 - 1.0. So 50% opacity would be like this:

```
.xxx {
    opacity: 0.5;
}

```

It's also not supported in many browsers (IE 6 & IE 7), but there are some workarounds. Examples here: <http://webdesign.about.com/od/css3/a/aa121306.htm>
It depends on your browser. Opacity works for Firefox and Safari. (use "opacity:" instead of "opacity :"). You also have to fix the opacity value, because this value must be defined between 0 and 1.

For IE, try :

```
filter: alpha(opacity=85)

```