[FONT=Verdana, sans-serif]The use of subscript tag <sub> is use for chemical compound in Chemistry while superscript tag <sup> is user for exponent power.[/FONT]
A human-driven reply is way too better than RTFM style with links, IMO. So that is a good answer on the question.
The <sub> tag defines subscript text and subscript text appears half a character below the baseline. Subscript text can be used for chemical formulas, like H2O. The <sup> tag defines superscript text and the superscript text appears half a character above the baseline. Superscript text can be used for footnotes, like WWW. Note: Based to W3C, whether SUB and SUP are intended to be used for stylistic presentation only. And if they are, it should be explicitly stated that they should not be used for exponents in mathematical expressions or in other contexts where it might change the meaning of a piece of text if SUB and SUP elements were presented as normal text.
