title_body: Why does the text in my aside display in my ebook? I'm trying to use the pop-up footnotes for that are now supported by iBooks see here. I can get the pop ups to work and it has the text that I want, but for some reason the text in the aside is also showing. 
  
  Why does it do that? I can't tell what I'm doing differently compared to the examples that I've seen. I put my markup below. I've also taken screen shots of my computer so that you can see what I'm talking about. See here and here
  
  &lt;html xmlns="http://www.w3.org/1999/xhtml" xmlns:epub="http://www.idf.org/2007/ops"&gt;
  &lt;head&gt;
      &lt;meta charset="utf-8"/&gt;
      &lt;title&gt;Hello World: My First EPUB&lt;/title&gt;
      &lt;link type="text/css" rel="stylesheet" media="all" href="stylesheet.css" /&gt;
  &lt;/head&gt;
  &lt;body&gt;
    &lt;p&gt;
        Alice was beginning to get very tired of sitting by her sister on the bank, and of having nothing to do: once or twice she had peeped into the book her sister was reading, but it had no pictures or conversations in it, 'and what is the use of a book,' thought Alice 'without pictures or conversation?'
        &lt;a href="content.html#l13" epub:type="noteref"&gt;1&lt;/a&gt;
    &lt;/p&gt;
    &lt;aside id="l13" epub:type="footnote"&gt;Alice estava começando a ficar muito cansada de sentar-se ao lado de sua irmã no banco e de não ter nada para fazer: uma ou duas vezes havia espiado o livro que a irmã estava lendo, mas não havia imagens nem diálogos nele, "e para que serve um livro", pensou Alice, "sem imagens nem diálogos?"
    &lt;/aside&gt;
  
    &lt;p&gt;
      &lt;a href="content.html#l24" epub:type="noteref"&gt;So she was considering in her own mind (as well as she could, for the hot day made her feel very sleepy and stupid), whether the pleasure of making a daisy-chain would be worth the trouble of getting up and picking the daisies, when suddenly a White Rabbit with pink eyes ran close by her.
      &lt;/a&gt;
    &lt;/p&gt;
    &lt;aside id="l24" epub:type="footnote"&gt;Então, ela pensava consigo mesma (tanto quanto podia, uma vez que o dia quente a fazia sentir-se sonolenta e letárgica) se o prazer de fazer uma coroa de margaridas valeria o trabalho de se levantar e apanhá-las, quando repentinamente um Coelho Branco com olhos rosados passou correndo perto dela.
    &lt;/aside&gt;
  
    &lt;/body&gt;
  &lt;/html&gt;
upvoted_answer: First of all, note that iBooks for OS X is very very buggy, and its behavior differs from iBooks on iOS with respect to many functions.
  
  Said that, note that "iBooks hiding &lt;aside&gt; elements" is an Apple quirk; any other reading system, in absence of relevant CSS rules or if they don't have a specialized behavior on elements carrying an epub:type, will display an &lt;aside&gt; as any other &lt;div&gt;.
  
  Have you tried applying a CSS rule (e.g., visibility: hidden) to your &lt;aside&gt;?
  
  BTW, for compatibility reasons, I tend to group the notes at the end of the XHTML file.
  
  Some links you might find useful:
  
  
  http://www.idpf.org/accessibility/guidelines/content/xhtml/notes.php
  http://www.pigsgourdsandwikis.com/2012/05/creating-pop-up-footnotes-in-epub-3-and.html
  http://www.heliconbooks.com/article/epubfootnote