var new_win;

function goback(){
history.go(-1);
}

function open_window(url,win_name,w,h,scroll)
{
var settings;
settings+='"toolbar=0, directories=0, menubar=0,"';
if(scroll!=null)
{
settings+='" scrollbars=yes, resizable=1,"';
}
else
{
settings+='" scrollbars=0, resizable=0,"';
}
settings+='"status=0, width='+w+', height='+h+'"';
close_window();
var new_win = window.open(url, win_name, settings);
new_win.focus();
}

function close_window()
{
 if(new_win  && !new_win.closed)
 {new_win.close();}
}