“Ruby text” is a new paradigm added to the CSS 3 specification (currently in draft). It allows an author to associate and align blocks or fragments of text with each other.
“Ruby” is the term used for a run of text that is associated with another run of text, referred to as the base text. Ruby text is used to provide a short annotation of the associated base text.
— CSS 3.0
<ruby>
<rb>WWW</rb>
<rt>World Wide Web</rt>
</ruby>
This would allow the design to place the ruby and the ruby text in the desired order, as shown here:
Common use cases will be for content written in Japanese or Chinese…although there are many examples of it in English as well.