Transparent and expandable wrapper div, how?

Answer 1

You will need an 1px high image slice for the transperncy and one for the rounded corders at the bottom

.background{
    background:url(/image/path);
}
.wrapper{
    background:url(/image/path/trans.png) repeat-y; 
    width:500px; 
    position:relative;
 }
.wrapper .bottom{
     background:url(path/to/image) no-repeat; 
     position:absolute; 
     bottom:0; 
     left:0; 
     height:20px;
}

.inner{
    background:#fff; 
    margin:10px;
}

I have made the widths and margins up. You should put in the right sizes yourself

Answer 2

#body {background: transparent url(background/image.png) 0 0 repeat-y;
}

#content-wrap {width: 60%;
               margin: 0 auto;
               background: transparent url(partially/transparent/60percent-opaque.png) 0 0 repeat;

}

#main-content {width: 90%;
               margin: 1em auto 0 auto;
               background-color: #fff;
}

#footer       {width: 90%;
               margin: 1em auto 0 auto;
               background-color: #fff;
}

This sets a partially-transparent .png image as the background for the #content-wrap section, with a solid color background for the divs (I've used #main-content and #footer, but they've got the same style so you could just use #content-wrap div and shorten the css a little.

<div id="content-wrap">
<!-- this is the outer wrapping div -->

<div id="main-content">

<!-- this I'm assuming is the main content portion -->

</div>

<div id="footer">

<!-- the name explains my assumption, I think... -->

</div>

</div>

...if you know that your audience will be using FF3.x (and probably webkit based browsers), you could use background-color: rgba(0,0,0, 0.6); to define the background-colour (red=0, green=0, blue=0, alpha=0.4 or 40% opaque (or 60% transparent) -the values being between 0 (entirely transparent) and 1 (entirely opaque).)

Using the rgba for colour prevents problems from using opacity to make the parent div transparent, while trying to make the children visible. But it's got limited use because of browser adoption, of course...

A working demo is over at my site: http://www.davidrhysthomas.co.uk/so/transparent.html