// JavaScript Document

function center(url,target){
x = (screen.width  - 640) / 2;
y = (screen.height - 480) / 2;
var pref='width=640,height=480,toolbar=0,location=0,directories=0,status=1,menubar=0,scrollbars=0,resizable=0';
op= window.open(url,target,pref);

op.focus();
window.op.moveTo(x,y);
}