DIV Appear Middle of Screen
<p>I have a button and I wanted (when click) to have a div appear in the middle of the screen.
The page it is on is a little long so where ever the user might be on the page - say half way down - when they click a button (that has this functionality) it will make a div appear in the  middle of the screen.</p>

<p>How could i do this?</p>
