Background: Blogger’s posting interface allows a sort of simple GUI that allows you to do common things like inserting a link, bolding or italicizing text with a keyboard combo or a button. For some reason though, Blogger inserts a <span style="font-style:italic;"> instead of a simple <em>, and similarly for bolded text. This script fixes that behavior, making your HTML that much prettier.
Update: Michael Kennan wrote a user script which basically does the same thing, and also demonstrates how to create your own keyboard macros within the Blogger post interface. So use his instead.