var win = null; 
function NewWindow(mypage,myname,w,h,scroll){ 
LeftPosition = (screen.width) ? (screen.width-w)/2 : 0; 
TopPosition = (screen.height) ? (screen.height-h)/2 : 0; 
settings = 'height='+h+',width='+w+',top='+TopPosition+',left='+LeftPosition+',scrollbars='+scroll+',' 
win = window.open(mypage,myname,settings) 
}