var width = document.compatMode=='CSS1Compat' && !window.opera?document.documentElement.clientWidth:document.body.clientWidth;
//   var height = document.compatMode=='CSS1Compat' && !window.opera?document.documentElement.clientHeight:document.body.clientHeight;

//alert(width); 
//alert(height);
ColonneLarghezza = ((width - 900)/2)-9;
//alert(ColonneLarghezza);

PosLestColDx = 900 + ColonneLarghezza; 
//alert(PosLestColDx);