function Popup(){
    this.html = '';
    this.title = '';
    this.resize = false;
    this.width = 400;
    
    this.init = function(){
        var bar = $('<div class="popup-bar"></div>');
        var close = $('<div class="popup-close">x</div>').click( function() {
                $(this).parent().parent().remove();
            });
        var title = $('<div class="popup-title">'+this.title+'</div>');
        var content = $('<div class="popup-content">'+this.html+'</div>');
        bar.append(close).append(title);
        
        var win = $('<div class="popup-window"></div>');
        win.append(bar);
        win.append(content);        
        $('body').append(win);
    };
    
    this.url = function(url){
        $.get(url,
            function(data){
                this.html = data;
                this.init();
            });        
    }
}

$(document).ready( function(){
    pop = new Popup();
    pop.url('/');
});

Uncaught TypeError: Object #<Object> has no method 'init'