A Google Web Search Help thread has complaints about a recent bug on the Google Advanced Search page.
By the bottom area where it says "You can also...", you can't also because there is some HTML/CSS bug that is preventing you from doing so.
Here is a picture of how that section renders on modern browsers:
As you can see, you really cannot also do more advanced searching because of the CSS issue with rendering the page.
Google is aware of the issue, Jessica from Google said in the thread:
This is indeed a technical issue and we're working on it. Stay tuned for updates.
Forum discussion at Google Web Search Help.
Update: On July 23rd this bug was resolved.
