var win = null; 

function popWin(mpage,mname,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 + ',resizable=no,titlebar=no,scrollbars=' + scroll  

win = window.open(mpage,mname,settings) 
win.window.focus()
//if(!win.window.focus) { win.window.focus(); } 
}