Also lesson 4:
Quote:変わる かわ) kawaru To change
Kana typo
Quote:沖 Oki Offing
That character's meaning is more accurately translated as "open water".
Quote:Today 今朝 Kesa
That means "this morning", not today. Today is 今日 which would also fit in this category.
Quote:Sweetness 甘味 Amami
That is the actual reading for those characters, so it doesn't fit in the category. Instead it is in the category of compounds that mix on and kunyomi.
甘い amai sweet (kunyomi)
味 mi flavor (onyomi, as seen in other words like 七味)
Quote:Minister 大臣 Otodo (DAIJIN)
While this is in the dictionary, it is almost always read as daijin (I've actually never seen it read otodo). You are better off listing common examples in such an early lesson.
As nadiatims said, I'm guessing you got some of these examples (the seasons) from literary furigana usage, not actual accepted words. マジ is another instance, but as I've actually seen that one in a couple manga I was willing to let it slide, though really you'd be better off picking an accepted word for teaching beginners. I recommend looking up words in a dictionary (NOT EDICT!!) before putting them as examples. Yahoo is a good one for finding pretty rare usages. If it's not in there, don't use it.
Unlike what others suggest, I support adding the background/historical/etymological info even to earlier lessons. Interesting tidbits like that gave me motivation when I was still a learner. I've seen some stuff on the basic lessons that even I didn't know yet. It might be a good idea to group it at the bottom in an Omake section as hyperlinked footnotes though.
I also think it's a bad idea to make up a new type of romaji that learners will see nowhere else. Just use hepburn (traditional hepburn-style long vowels since it's a pain to add macrons manually). Better yet, teach the major romanization systems and maybe use them to introduce the kana (along with sound files for pronunciation), but never use them in the actual lessons. Using romaji as a crutch always slows learners.
You might want to consider turning the entire site into a moderated wiki if you really want a lot of help. You could also make use of bots to automatically generate links to linguistics terms etc. If you do so you should put the site under a creative commons license though.
Edited: 2011-11-29, 3:27 am