Hivewallet.com has officially closed down but there is an easy way to recover any bitcoins you may have had saved in your Hive wallet.
In September of 2015 the founder of Hive announced that after a year of very little development all development had officially stopped. In April of 2016 the hivewallet.com website officially closed down.
Because of their pro-privacy stance there was no way for Hive to notify all users, and some of us only became aware of it when we tried to log in only to learn it was no longer possible. The immediate thought is almost certainly "how do I get my bitcoins back?".
There are some approaches outlined on github, but most are somewhat daunting. There is however a much simpler approach to recovering your bitcoins from Hive documented with step by step instructions.