This element contains the Ruby Text (helper content) for the Ruby Base (RB)
content. Internet Explorer renders Ruby Text content above the Ruby Base
content in a smaller font. The Ruby Text element is optional within the RUBY syntax.
If the RB/RT order is reversed, the RT content will not receive Ruby Text special
rendering.
Browser Peculiarities
Internet Explorer 5.0 Beta 2: Using block elements in the Ruby
Base places the Ruby Text content BELOW the Ruby Base. This does not seem
to be the intention of the implementation of Rubies, so the behavior may change by
the final release.