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: 
For cross browser opacity, you want:

```
{ 
    -moz-opacity:.50; 
    filter:alpha(opacity=50); 
    opacity:.50; 
}

```
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)

```