They are static attributes of the object. Lets say you want to write out the date and time of the last modification to your page onto the screen. Whenever you update your page and save it, this script will display the date and time of this occurrence. Its a static attribute of the current document. In order to show this property, we used the non-static method to write this information out.
Lets try playing around with another document method then.
Ok, maybe not so useful like this, but you get the point. As you learn more about JavaScript, you will bump into more objects. Tutorial introduction - FAQs about this language. NO PART may be reproduced without author's permission.