Question

I have a page middle aligned with margin: 0 auto; which is the page content. I need my navigation to have also margin-left: auto; but also needs to go until the end of the screen, even if the user re-size or zoom out the page, this nav must really go until the end.

Now I have something like this:
http://jsfiddle.net/Dc7XK/

Answer 1

I would suggest using a containing div like this:

<div id="outter">
  <div id="container">
    <div id="navigation">
      lorem ipsum dolor 
    </div>
  </div>
</div>

And the css:

#outter{
  width:100%;
  background-color:#00ff00;
}
#container{
   width:500px;
   margin:auto;
   margin-top:20px;
   background-color:#ff0000;
   padding:20px;
}


#navigation{
  width: 100%;
  background-color: black;
  height:16px;
  color:#fff;
}

Set your outer div to 100%.
Then have a containing div the width you want the page with margins set to auto. Finally, have your navigation set to 100% width of the container! Boom.

http://jsfiddle.net/Dc7XK/2/

I hope this is what you are after!