This is a draft compilation of a majority of the tags from the kml file (that I know about). Feel free to look at this and make suggestions.

Background:
I have been working on trying to figure out the KML file structure. (Bsically, what you can and can't do in Keyhole.) Most of this information was pulled from other people's postings (OPP). The rest of it came from advice from others. I had posted earlier forms of this in a different forum HERE; however, after reading quite a few more postings, I think this forum is probably the most relevant place to put this.

I will continue to update this file with anything that someone sends me. If there is anything wrong in this file please let me know so I can try and update this file.

NOTE: In order to see most of the comments, you need to view the kml file in notepad.

Edit: I fixed the image problem.
Edit: I am trying to fix the problem of geometries showing up incorrectly in this post.
Edit: I added some more explinations, and I added polygons.
Edit: I added Ink_Polaroid's Circle Tool to this file. See this.
Edit: I added the Screen Overlays from Seer's post.

Contents:
Lines (color and width)
GPS routes
Polygons (with and without holes)
Circles (as filled polygons)
Ground Overlays
Screen Overlays
Network Links
HTML in the description field