Your comments

It was reported that entering the user name without "@me.com" resolves this issues. (see comments below)
Hello, "%" and ";" are actually in the row of additional keys, but you need to scroll the row horizontally to get to them.
So, entering the username without @me.com solved the http status 402 problem for you?
Also on Wikipedia: "As an example of its use, however, Apple's MobileMe service generates a 402 error ("httpStatusCode:402" in the Mac OS X Console log) if the MobileMe account is delinquent." http://en.wikipedia.org/wiki/List_of_HTTP_status_codes#402
Hello, according to the list of HTTP Status Codes, code 402 means "Payment Required". See http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html

I'm not sure why that is returned. Can you connect to your iDisk on your Mac? Are you absolutely sure you're using the correct login details?
One thing that would really help me: can you please send me one or two of those html files with many Japanese characters so I can test the performance with them? You can mail it to support@textasticapp.com

Thanks for the link to the ForMatKonaVe font. I've downloaded it and the readme says:

ライセンス
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この作品は、クリエイティブ・コモンズの帰属-同一条件許諾(Creative Commons Attribution-ShareAlike) 2.5ライセンスの下でライセンスされています。
この使用許諾条件を見るには、

http://creativecommons.org/licenses/by-sa/2.5/
http://creativecommons.org/licenses/by-sa/2.5/deed.ja

をチェックするか、クリエイティブ・コモンズに郵便にてお問い合わせください。
住所は:559 Nathan Abbott Way, Stanford, California 94305, USA です。
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これは元にした小夏フォントと同じライセンスです。


So, according to Google translate, the font is under the same creative commons license as Konatsu and I think I could use that.

I will try out if it works with Textastic and if it does, I will add it in an update.