function fixSize(o){
    var sw = screen.availWidth*0.8;
    var sh = screen.availHeight*0.75;
    
    var r1 = sw/sh;
    var r2 = o.width/o.height;
    var s = r2>r1 ? sw : sh;
    
    o.parentNode.href=o.parentNode.href.replace(/\*size\*/,s);
}
Event.observe(window,"load",function(){
    var l = document.getElementsByTagName("a");
    for(var i=0;i<l.length;i++){
        if(/lightbox/.test(l[i].getAttribute('rel'))){
             fixSize(l[i].getElementsByTagName('img')[0]);
        }
    }
});