function nav(url,winX,w,h){
var url=url?url:'../nav.html';
var winX=winX?winX:'Image';
var w=w?w:250;
var h=h?h:250;
LeftPosition=(screen.width) ?(screen.width-w)/2 : 0;
TopPosition=(screen.height) ?(screen.height-h)/2 : 0;
win=window.open(url,winX,'toolbar=0,location=0,directories=0,status=no,menubar=0,scrollbars=0,resizable=yes,width='+w+',height='+h+',top='+TopPosition+',left='+LeftPosition);
if(win.window.focus){win.window.focus();
win2.creator=self}
}