title_body: Why does the text in my aside display in my ebook?
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