var myrules = {
    'a.popup500' : function(el) {
        element.onclick = function() {
            if( el.target == '_blank' ) {
              return true;
            } else {
              window.open( el.href, 'popupwindow', 'scrollbars=yes,width=500,height=600');
              return false;
            }
        }
    },
    'a.popup600' : function(el) {
        element.onclick = function() {
            if( el.target == '_blank' ) {
                return true;
            } else {
                window.open( el.href, 'popupwindow', 'scrollbars=yes,width=600,height=600');
                return false;
            }
        }
    },
    'a.popup660' : function(el) {
        element.onclick = function() {
            if( el.target == '_blank' ) {
                return true;
            } else {
                window.open( el.href, 'popupwindow', 'scrollbars=yes,width=660,height=600');
                return false;
            }
        }
    }
};

Behaviour.register(myrules);