This is very important to remember for a few reasons. Any object within the DOM that is not named or given an "id" can be accessed "hollywood style" in order of appearance on the document. For instance if I wanted to accessthe data typed in by the user in the first element of a form that was the first on a page I could get at it by document.form.element.value
It is not required but does give you more control over size etc. of the new window you are opening.