Oh, erm was going to warn, it's a Java applet.
(Java sux btw)
Um, well if you're still using FireFox, I guess you need to install Java for that page to display the problem and let you play the moves.
Don't worry about the mate in 61 thing; that was just a calculation I made when going through the problem. It could be virtually any number of moves you want, really. No chess engine is going to be
able to solve this problem without a ton of hints from a human mind.
If you want to install Java to FireFox's plugin container, I got my installation from here.
http://www.oracle.com/technetwork/java/javase/downloads/jre-7u2-download-1377135.htmlbut the stable Sun Java 6 was a bit less crash-prone on other websites, but wth, so far it's working ok for me