Steemd.com is the block explorer of STEEM where you can keep a detailed track of your activity on steemit.com as well as when you are mining for STEEM with your computer. It seems that the website went down a little while ago (not the first time happening) and is currently not opening, so at the moment you cannot keep track of the extra statistics and information that it provides... unless of course you move to an alternative service.
Hopefully the problem will be resolved quickly and the website will be back online shortly, but meanwhile if you are wondering where you can keep a track of your account while steemd.com is back online, you can check the SteemStats.com website made by user 
Steemstats offers users of steemit.com a great interface for monitoring your activity and progress - who you follow, where you have voted, how much is estimated to earn from posts and votes and many other useful features. Unfortunately the part that is not being covered that is available on steemd.com is for the users mining STEEM, so you will have to do without that functionality for a bit.
