It's a mirror of the old Castle Quest from the old Caverns of Blood. Thanks to NukeA6 for providing an entire backup of Castle Quest!
Sadly, most web browsers have moved on and a lot of the fun stuff doesn't work anymore. I'd recommend finding a Windows XP VM (or better a Windows 98 VM) and visit using IE6. Modern Firefox is marginally better, but it's not remotely the same.
Also, the game doesn't work outside of 640x480 resolution due to tiling issues. You might be able to shrink the window down, but you're better off with a VM
Anyway, onward to Castle Quest
Or go into the Caverns of Blood