From a composer and classically trained musician:
Poor neglected C clef (used by violas and sometimes trombones)
Treble clef (also called G clef) does not always signify melody. It's used mainly by instruments whose range is largely above middle C ... or by voices (like a tenor singer) whose natural range is easiest to signify in a treble range. For instance, a cello (who uses bass clef ... also called F cleff) is often given melodies in string music.
May want to mention that treb. clef has its bottom circle around the G and bass cleff has the dots around F ('cause these guys can move up and down the staff, yo)
being nit-picky, flats and sharps should be thought of as "down" and "up" respectively, not "back" and "in front"
middle C is actually C4 scientifically and C' in helmholtz.
You left out the symbol for naturals.
Would've been nice to include key signatures (at least the concept) and time signatures as well (again, the concept). Maybe eigth, quarter, half and whole notes? Or is that the next tutorial? :P
you may want to mention that chords in guitar tab are stacked together. Tab also has the disadvantage in lack of precise timing. You kind of have to know what the song sounds like already in order to follow tab.
All in all, decent starting tutorial. Would've been nice to put sounds to the notes (maybe clickable?) Also, to hear what the tab sounds like and the sounds each of the individual guitar strings make. This way you start 'em early on ear training and those that play by ear can associate what they already know with the visible notes.