The need to use the HTML5 <ruby> tag is emphasized when Ruby annotations are placed within the HTML document. Ruby annotations are those which are used to emphasize the East Asian typography which has different pronunciations. The HTML5 <ruby> tag is best paired with <rp> or <rt> tags to be able to make the characters much clearer for the users.
The HTML <ruby> tag is not yet introduced in HTML4.01 and is a new addition in HTML5. Even so, it is easily recognizable by the different web browsers like Safari, Opera, Firefox, Internet Explorer and Google Chrome. The HTML <ruby> tag has no complications with the Event Attributes and Global Attributes because it is compatible with these.