When you say the web page resource has source code of it's own - where is that? What do you mean by that. Do you mean I can't change it or Ican.
I really want to be able to have coding and css capabilities to really customize my layout and styles.
Is there perhaps a plug in or module that is useful for what I am looking to do? I have been trying to look at the Moodle Docs for more info on this.
http://www.w3schools.com/css/default.asp has some examples of different ways to use css. If you need to use css inside some document you can use editor to add some tags and for example tinymce (the coming default editor in moodle 2.0) has a style plugin http://korpelainen.net/test19/mod/book/view.php?id=66&chapterid=18
In htmlarea you can press <> in editor and write or copy and paste html and css from any other wysiwyg editor as well (for example from http://tinymce.moxiecode.com/example_full.php?example=true )
You may look at css files of moodle and take some class from them and use it with tags like (after pressing <>):
<p class="unread">test 1</p>
<p style="color: red; text-align: center">test 2</p>
test 1
test 2
and so on. If you upload some web page to site or course files it can have links to custom css files inside the page itself and you may also embed web pages inside iframes to show those pages in a sort of "window" - iframe...
EDIT: There is a big difference if you add a link to a file (html page) http://docs.moodle.org/en/File_or_website_link
or compose a web page http://docs.moodle.org/en/Web_page
Check also http://moodle.tokem.fi/mod/book/view.php?id=16397&chapterid=7918 as a nice tutorial...