user14084: No computer at the moment, so I have Wallets at two independent websites.  I sent millibits from one wallet to the other.  I hear that you have to use your private key to do that.  So, I guess that site created the private key for me, and they control it?  I certainly don’t know what it is.

user11253: Yes, when you use an online wallet service, you are trusting the website operator to generate and maintain your private key(s) for your account. 
There is a saying that goes something like, "Unless you hold your own private keys, your bitcoins aren't really yours."

14084: <p>No computer at the moment, so I have Wallets at two independent websites.  I sent millibits from one wallet to the other.  I hear that you have to use your private key to do that.  So, I guess that site created the private key for me, and they control it?  I certainly don’t know what it is.</p>
 11253: <p>Yes, when you use an online wallet service, you are trusting the website operator to generate and maintain your private key(s) for your account. </p>

<p>There is a saying that goes something like, "Unless you hold your own private keys, your bitcoins aren't really yours."</p>
