There have been several queries on this over the weeks. It was taken down due to using resources from other authors without permission. It's still being updated, but won't be available on Nexus anymore and I'm pretty sure linking to it from here is prohibited as well due to the nature of the content.
If you need an alternative, http://skyrim.nexusmods.com/mods/24913 is now the go-to monster compendium mod. And I daresay it's superior due to less bloat and more carefully thought out additions. No more sharks swimming around in rivers, for example.