The HTML5 <sub> tag is used for making sure that the character will appear half a character below the baseline. Typically, the HTML5 <sub> tag is used for incorporating chemical equations within the HTML document. In some languages, like French, the HTML5 <sub> tag is used to indicate abbreviations.
When the document has to have the HTML5 <sub> tag, it is easy to use it along with the Event Attributes and Global Attributes in HTML5. Hence, that author should not worry about complexities. The HTML5<sub> tag is easily recognized by the major web browsers like Internet Explorer, Opera, Safari, Google Chrome and Firefox.