function Pop(myurl) {
open(myurl, '_blank', 'width=630,height=630');
return false;
}

var alllinks = document.getElementsByTagName('a');
for (i=0; i < alllinks.length; i++) {
    if (alllinks[i].className == 'pop') {
        alllinks[i].onclick = function() {return Pop(this.href);};
    }
}