Event.observe(window,'load', function(){
   var scr = document.viewport.getDimensions();
   $('midm').style.width = (scr.width - 460) +'px';
   $('midm').style.height = (scr.height - 150) +'px';
   $('midm').style.display = 'block';
   if($('princ')) $('princ').style.height = (scr.height - 150) +'px';
});

Event.observe(window,'resize', function(){fireEvent(window, 'load');});