Question

I’m trying to put an empty div on the right side of my content div. This div is empty because I’ll use it to put a background image.

Take a look: http://jsfiddle.net/V9XtN/3/

I want that the div bellow take all available space, on the left side of the blue div.

#ConteudoDireito {
width: 35%;
height: 100%; 
float: left;
overflow: hidden;
background-color: Red;
}

Answer 1

One option: add position:absolute; and right:0; to #ConteudoDireito :

http://jsfiddle.net/V9XtN/6/

If you later fill the div with content, there is no need for this, since the div will expand to the content height, so you can change it back to what you have now.