var popupWindow=null;
function popup(mypage,myname,w,h,pos,infocus){

if (pos == 'random')
{LeftPosition=(screen.width)?Math.floor(Math.random()*(screen.width-w)):100;TopPosition=(screen.height)?Math.floor(Math.random()*((screen.height-h)-75)):100;}
else
{LeftPosition=(screen.width)?(screen.width-w)/2:100;TopPosition=(screen.height)?(screen.height-h)/2:100;}
settings='width='+ w + ',height='+ h + ',top=' + TopPosition + ',left=' + LeftPosition + ',scrollbars=no,location=no,directories=no,status=no,menubar=no,toolbar=no,resizable=no';popupWindow=window.open('',myname,settings);
if(infocus=='front'){popupWindow.focus();popupWindow.location=mypage;}
if(infocus=='back'){popupWindow.blur();popupWindow.location=mypage;popupWindow.blur();}
}