Question

<a href="#dialog" name="modal">Simple Modal Window</a>

<div id="boxes">
 this should be under modal

    <!-- #customize your modal window here -->

    <div id="dialog" class="window">
        <b>Testing of Modal Window</b> |

        <!-- close button is defined as close class -->
        <a href="#" class="close">Close it</a>

    </div>
    <br />
     this also
    <!-- Do not remove div#mask, because you'll need it to fill the whole screen -->
    <div id="mask"></div>
</div>

LIVE: http://jsfiddle.net/ruwmh/

How to make that modal screen be on all screen? Now this isnt o

Answer 1

You should change the CSS like this

#mask {
  position:absolute;
  z-index:9000;
 /*add left and top to position to upper left */   
 left:0;
  top:0;
  background-color:#000;
  display:none;
}

fiddle here http://jsfiddle.net/ruwmh/1/