According to w3.org first-letter pseudo class works only with block level elements. Here is a paragraph from w3:
The :first-letter pseudo-element must select the first letter of the first line of a block, if it is not preceded by any other content (such as images or inline tables) on its line.
Code with label that works across all browsers:
Note, that there should be a space character between first-letter and curly bracket. Otherwise it will not work in IE6. So if you want to punish IE (or your users), use: