How do you remove numbering from headers when exporting from org-mode?

The basic org-mode headers

* Heading
** Sub-heading
* Another Heading

get converted to html like this

1. Heading

1.2 Sub-heading

2. Another Heading

(but imagine them larger and in h1 h2 fonts and sizes). How do you turn this off so that the headings are not numbered in the output html?

Oleg's answer allows you to disable section numbering for all exports at all times. However if you only want to disable numbering on export for a single file you can use the following:

#+OPTIONS: num:nil

If you want to limit it to only a certain depth you can replace nil with an integer specifying up to which headline you want the numbers to appear. For example #+options: num:1 would turn your sample into:

1. Heading

   Sub-Heading

2. Another Heading

See Export Setting for the details and other export options that can be set on a per-file basis.
See HTML Specific Settings for HTML specific ones.

You can customize the org-mode.

M-x customize-mode

org-mode

Then you choose Org Export/Org Export General/Org Export With Section Numbers

As an alternative put the following in your .emacs

(setq org-export-with-section-numbers nil)