One thing that you may have noticed is that whenever you refresh the page you get a new song name, this may seem random but it's not and with a little bit of googling you'll notice that these songs were performed by elton john. Now that we know that, we have to find how the music collection is organized on the server, after many tries I found that the songs are organized in letter by letter directories, trying all the different possibilities is a waste of time because we already know where to look for our password, it's in http://www.hackthissite.org/missions/basic/11/e/l/t/o/n/ but when you get there, this directory may seem empty, but actually it's not, there is a hidden file in it and it's named ".htaccess", this file allows a directory level configuration of the web server (In this case Apache). When you open the .htaccess file you'll see this interesting instruction:
IndexIgnore DaAnswer.* .htaccess
this tells to the web server to exclude these two files from the directory listing. Now we know that our password in the "DaAnswer" file, when you open the file you'll get something like
The answer is easy! Just look a little harder.
You have to take it literally, cause in this case the answer is "easy" (without the quotes), now go to the index.php, submit your anwser and the "go on" link will appear, you have completed the 11th basic mission.