Level Fifteen
'hit the keys'

The key hint here is in the source code (the password hint reads 'you are on your own'). It reads

!-- [1] 4 [2] 1 [3] 6 [2] 3 [1] 9 [3] 7
[2] 2 6 [1] 8 5-->

'Hit the keys' and URL 'rusty board' imply this has something to do with the keyboard. Let us try to interpret the numbers as coordinates of keys. Notice that all bracketed numbers are between 1 and 3, so those are possibly rows and the other numbers might be the number of the key counted from left to right or right to left. The first interpretation gives

random
shit

and this works. On to Level Sixteen
Until then