function popImage(_which, _hi, _wi, _maxhi, _maxwi){
    
    var maxwi = 750;
    var maxhi = 500;
    
    var wi = Math.min(_wi, _maxwi) + 20;
    var hi = Math.min(_hi, _maxhi) + 20;
    
    var leftPos = (screen.width) ? (screen.width - wi) / 2 : 0;
    var topPos = (screen.height) ? (screen.height - hi) / 2 : 0;
    
    window.win = window.open(_which.href, 'imWin', 'height='+hi+',width='+wi+',top='+topPos+',left='+leftPos+',scrollbars=1,resizable=1');
    return false;
}