Even though notifications have made it into the latest chrome stable release (v4) they cannot be used unless permission is granted only by executing the requestPermission method using a javascript: link. Your current status is:

A simple notification, using the createNotification() method, we pass in 3 parameters: an icon url, title and body text. To see the notification in action view this page in Chrome 4+

A custom notification, using the createHTMLNotification() method, we pass in 1 parameter: url. This will be passed a html page which can be styled up any way you like. This example loads in a random tweet, every 15 seconds, about HTML5 or CSS3.