"Document" is a Class that is part of the DOM (Document Object Model). This "library" is referenced automaticaly by the browser of the OLPC station and you don't need to add anything in the program to use it.
You don't need to create any object for this Class because it will have only one stantialization for a page. You will use the "prefix": document to call its elements.
write(String) String can be HTML tags. It's commomly used to write dynamically a page.
cookie [= String] Is R/W. Used to write or read a cookie. The String is: "name-of-cookie = value; expires=expiration-date" An example, of code, reading the data from a textbox to a cookie "dynamic1"; then = new Date(); then.setTime(then.getTime() + 60*60*1000) //cookie available one hour document.cookie = "dynamic1="+document.form1.tb1.value+";expires="+then.toGMTString(); (object of the Class Form) Normaly we have a chain of objects, because a property of the Class Form can be an object of the Class TextBox etc. By example: we can capture what was typed at a textbox with: document.form1.tb1.value bgColor = Color define the background color of the page.
Link to the Classes: Form