Hi, Vincent!
According to my logic, that is ... :-)
I see your concern, but Stepan has submitted clear HTML source for these dropdowns, and the links follow the URI syntax. The search engine does not navigate the page being analyzed in a graphical web browser - it pulls the raw source of the page, analyzes it, perhaps via regex, finds all links on the page and starts new indexing sessions for these URIs. If the URI is valid, it should follow it. Why do you think many webmasters put the following right before the closing </BODY> tag:
<a href="http://www.somesite.com/indextop.php"> </a>
This makes the web crawler analyze a specially prepared "top" index which has more meta information than the main index.
I understand that perhaps this is because the webcrawler searches for <a href=" and </a> delimiters before spinning off a new request. But it is possible to fix this by making an invisible layer, just as I said. This layer will not be processed by old browsers and will still present the info in the way a web spider expects it.
Best regards,
Stas