Nested ordered list won't display specified type

In a post, I've got an ordered nested list that is supposed to show numbers at the first level, then letters at the nested level. In WP edit mode, it works fine. I've got <ol type="a"> starting the nested level, and in visual edit mode, it shows a lettered nested list. However, in preview and after publication, it displays numbers, not letters, at both levels. I was able to correct it via firebug but when I tried to make the same fix to the real file, it didn't work. Firebug shows the following, which when deactivated (in firebug only), fixes it - Style.css, line 128 -

* ol li {
list-style-type: decimal;
}

What's the problem?