function MostrarDemo()
{
   if (document.getElementById("demo").style.display!="block")
   {	   
	   //SetVerticalMiddle (document.getElementById("demo"),220);
	   document.getElementById("demo").style.display="block";
   }

}
function cerrardemo()
{
    document.getElementById("demo").style.display="none";
}

function SetVerticalMiddle(element,desp) 

{

    var y = 0;
    var height = getClientHeight();//clientBounds.height;
    if (document.documentElement && document.documentElement.scrollTop) {



        y = document.documentElement.scrollTop;

    } 

    else { y = document.body.scrollTop; }

    y = Math.max(0, Math.floor(y + height / 2.0 - element.offsetHeight / 2.0 ));

    y=y-desp;
    element.style.top = y + 'px';

}


function getClientHeight() {

    var clientHeight;

    switch(navigator.appName) {

    case "Microsoft Internet Explorer":

        if (document.documentElement && document.documentElement.clientHeight)

            clientHeight = document.documentElement.clientHeight;

        else if (document.body)

            clientHeight = document.body.clientHeight;

    break;

       clientHeight = document.documentElement.clientHeight;

    break;

     case "Safari":

        clientHeight = window.innerHeight;

    break;

    case "Opera":

        clientHeight = Math.min(window.innerHeight, document.body.clientHeight);

    break;

    default:

       clientHeight = Math.min(window.innerHeight, document.documentElement.clientHeight);

    break;

    }

    return clientHeight;

}