amazon kindleにて変換できるファイルの種類。
＃以下、free.kindle.comにてファイルを変換しようとした際のリターンメールより。

＜補足＞
　ちなみに、htmlファイルは従来のバージョンではブラウザにて読めたらしいが、
　現在の３で試したところ読めなく、ネットでもいろいろと探したところ、
　どうも読めなくなった模様。

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The Kindle Personal Document Service can convert and deliver the following types of documents:
Microsoft Word (.doc)
Rich Text Format (.rtf)
HTML (.htm, .html)
Text (.txt) documents
Archived documents (zip , x-zip) and compressed archived documents
Mobi book

Images that are of type JPEGs (.jpg), GIFs (.gif), Bitmaps (.bmp), and PNG images (.png).
Adobe PDF (.pdf) documents are delivered without conversion to Kindle DX, Second Generation and Latest Generation Kindles.

The following document types are converted and delivered on an experimental basis:
Microsoft Word 11 (.docx)
Adobe PDF (.pdf) for First Generation Kindles

If the document(s) that failed belonged to one of the above document types, please ensure the document is not password protected or encrypted. Note that the Latest Generation Kindles support password protected PDFs.

You can learn more about transferring personal documents to your Kindle in our help pages:
http://www.amazon.com/kindlepersonaldocuments/