the addEvent() and addLoadEvent() functions simply manage all your functions that are attached to the onload event - very useful if you have multiple functions. As the onload event handler can only hold one function at a time, addEvent() and addLoadEvent() effectively creates a queue of functions to be executed in order when the page loads.
For external links i use the icon suggested in css mastery - its on the cover of the book
http://www.cssmastery.com/