Hello.
Thanks for your answers, specially to Hitch. I downloaded both Flight Crew and Sigil, and I could solve most of the validation errors.
I was looking for an ePub editor, and Sigil was the one.
For ePub creators I recommend to use BookCreator, because it is very simple to use. It creates the file and its structure from Word and you don't have to know about Epub code to create the chapters. To polish the ePub you need Sigil, because Epub validators are very strict, and any unlinked html code you have in your file will block it to be published. I agree with Hitch in that.
However, Flight Crew approved my file with some errors.
The validator that really gave me certainty that my file was correct was "ePUB Validator". Available here:
http://www.ebook-tool.com/epub-validator.htm
Thanks to this last test my ebook was approved to be published in the Ibookstore.
Again, thanks to =X=. Your macro is very helpful and easy to use.
I hope this information helps to new authors.