PROPERTIES OF WINDOWS
window object represents an open window in a browser.
If a document contain frames (<frame> or
<iframe> tags), the browser creates one window object for the HTML
document, and one additional window object for each frame.
The Event Object
Within an event handler, you can do pretty much
anything you want with your script code. Chances are, you'll want to perform
some action related to that event depending on one or more factors.
click mousedown mouseup mouseover mouseout
dozens of different events constantly firing and moving up and down the
document tree, the real trick to using event handlers is in figuring out what
event to catch, where to attach the handler and how to process it.