HTML Markup
In 2001, the W3C published the Ruby Annotation specification for supplementing XHTML with ruby markup. Ruby markup is not a standard part of HTML 4.01 or any of the XHTML 1.0 specifications (XHTML-1.0-Strict, XHTML-1.0-Transitional, and XHTML-1.0-Frameset), but was incorporated into the XHTML 1.1 specification, and is expected to be a core part of HTML5 once the specification becomes finalised by the W3C.
Support for ruby markup in web browsers is limited, as XHTML 1.1 is not yet widely implemented. Ruby markup is partially supported by Microsoft Internet Explorer (5.0+) for Windows and Macintosh, supported by Chrome, but is not supported by Mozilla, Firefox (though see below), Konqueror or Opera. The WebKit nightly builds added support for Ruby HTML markup in January 2010. Safari has included support in version 5.0.6.
For those browsers that don't support Ruby natively, Ruby support is most easily added by using CSS rules that are easily found on the web.
Ruby markup support can also be added to some browsers that support custom extensions. For example, an extension allows Netscape 7, Mozilla, and Firefox to properly render ruby markup under certain circumstances. This extension is freely available for users of these browsers.
Ruby markup is structured such that a fallback rendering, consisting of the ruby characters in parentheses immediately after the main text, appears if the browser does not support ruby.
The W3C is also working on a specific ruby module for the upcoming CSS level 3.
Read more about this topic: Ruby Character