From the Smashwords blog:
We updated the Smashwords Style Guide today to include improved instructions for building linked Tables of Contents, controlling your NCX, building intra-book links for footnotes and endnotes, and troubleshooting. The new instructions are included in an expanded Step 20. Download the latest Style Guide here.
Separately today, we reached an exciting milestone. Today, the 100,000th copy of the Smashwords Style Guide was downloaded at Smashwords.com. Thousands of additional copies have been downloaded through our retail distribution network and Amazon.