function book_for_top(url)
{
NLeft = Math.round(screen.width/2 - 234);
NTop = Math.round(screen.height/2 - 115);
var win2;
win2 = window.open('','Preliminary_Design', 'menubar=no,toolbar=no,resizable=no,width=468,height=230,left=' + NLeft + ',top=' + NTop);
win2.location=url;
}