It is called
drop-caps. It can be done in html by making the <font size=xxx> tag set the font bigger than the surrounding text. That is actually only a simulation, as html doesn't actually do it correctly. Another way to do it is to use CSS to set a <span> tag to a larger size. A third way to do it is to use a graphic image of the large letter - that is the way to most closely imitate typeset printing.
BTW, initial caps is the editorial term for the first letter of each word being capitalized. Superscript (which can indeed be done in html) is the term for small text raised, as in a footnote or mathematical notation. Putting it down lower is called subscript..