When you wish to number a list, especially for reference purposes, use an enumerated list. The first letter is usually in upper case.
The relevant command is similar to the itemize one, but substitutes enumerate for itemize. Enumerated lists can be indented and different numberings (1, 2, ... or (a), (b), ...) and so on will be generated for you automatically at each level. However, this does not happen in the HTML version where a single numbering scheme is used at all levels of indentation at present.
Here is how the above list was generated:
\begin{enumerate} \item This is the first item; \item And this is the second; \begin{enumerate} \item This is the first item of a new indented list; \item And this is the second thereof; \end{enumerate} \item This is the third item of the first list. \end{enumerate}