Scratch

If you enter 3d in the Forum Search box and click the button, you will get the following response:

"You have to enter at least one keyword and/or an author to search for."

If you go to Google and search on the following keywords, you will get hundreds of hits on forum postings that contain the text "3d"

3d site:http://scratch.mit.edu/forums/

In addition, using Google's advanced search capabilities, you can make your search more sophisticated by using logic and other advanced features in the search.

Therefore, Google provides an alternative, and in some cases better way to search the Scratch forums than is provided by the Forum Search box.  Just go to Google and enter the following:

keyword1 keyword2 keyword3 ... keywordX site:http://scratch.mit.edu/forums/

By the way, this is true not only of the Scratch forums, but of many of the forums that you will find on the web.

Don't forget to include the site designator to limit the search to the Scratch forums.  If you poke around in the file structure of the forums, you may also find other characteristics that will allow for even more sophisticated searching using Google.