// Popup Window

function centeropen(url, winwidth, winheight){
 var centerwin=window.open(url, "", "toolbar=1, resizable=1, scrollbars=1, status=1,menubar,addressbar")
 centerwin.resizeTo(winwidth, winheight)
 centerwin.moveTo(screen.width/2-winwidth/2, screen.height/2-winheight/2) //center window on user's screen
}