To give an ordered list letters instead of numbers (and still validate to XHTML 1.0 Strict) use the following style:
<ol style="list-style-type: lower-alpha;"> <li>banana</li> <li>orange</li> <li>peach</li> </ol>
It will look like this:
- banana
- orange
- peach
Don't use the type attribute, it's been discontinued.