The annotator requires a frames-capable browser.
Current versions of Netscape (2+), Internet Explorer (3+), Opera, HotJava, and even Lynx support frames. You have plenty of choices.
Lynx users, the main text with links to notes is here, the center-right frame. Notes will appear as the alt text to the note and link marker images. Use this link or the "add a note" at the bottom of the page to annotate.