Background Transparency with Opaque Text

I tried searching for a similar thread, but was unable to find anything.

I'm trying to make the backgrounds of my content divs 70% transparent using the following:

.transparency {
filter:alpha(opacity=70);
-moz-opacity:0.7;
-khtml-opacity: 0.7;
opacity: 0.7;
}

Unfortunately, this is also making the content within those divs use the same opacity. I tried nesting another div inside using the following:

.opaque-text {
filter: alpha(opacity=100);
-moz-opacity: 1.0;
-khtml-opacity: 1.0;
opacity: 1.0;
position: relative;
z-index: 2;
}

But it does not seem to be working. I feel like this should be a simple fix, and I'm missing something obvious. I know I can always use a .png as a background image, but I'm trying to do this in pure CSS if at all possible.

Thanks!