user3344: I sent some bitcoins to an address.
The transaction seems to have been executed, and I do have a transaction hash; but when I search for it on http://blockchain.info/ it says "transaction not found"... 
where did it go?!
Should I be worried? The transaction was processed at 04/10/2013 20:38 - about 3 hours ago now. Isn't that too long?
I did not add any transaction fee, because there is no option for it.
The transfer was started from bitcoin-central.
update
Since the money finally arrived, I guess i could slightly rewrite the question such as:
How can there be such a (long) latency from the moment a transaction is executed (eg. I get a transaction hash) to the moment the transaction is seen on the system (eg. blockchain.info)? 
how can it be that it is not showing (hours later, not seconds later)?
How can I know the hash I got is valid/real?

user153: Your account at Bitcoin-Central is a hosted (shared) E-Wallet.
This means that you are not withdrawing your bitcoins, you are sending a request to the E-Wallet provider to withdraw your bitcoins.  
If for whatever reason that E-Wallet provider is unable to service that request immediately (for example, their hot wallet is depleted and they need to wait until business hours to get access to the bank vault to be able reload from cold storage) then the site might provide to you confirmation of your withdrawal request but that doesn't mean a Bitcoin transaction was broadcast to the network.
If you have a transaction hash, and that transaction is broadcast, then you should see it on Blockchain.info. 
Otherwise, the problem is with the E-Wallet provider.

3344: <p>I sent some bitcoins to an address.
The transaction seems to have been executed, and I do have a transaction hash; but when I search for it on <a href="http://blockchain.info/" rel="nofollow">http://blockchain.info/</a> it says "transaction not found"... </p>

<p>where did it go?!</p>

<p>Should I be worried? The transaction was processed at 04/10/2013 20:38 - about 3 hours ago now. Isn't that too long?</p>

<p>I did not add any transaction fee, because there is no option for it.</p>

<p>The transfer was started from bitcoin-central.</p>

<p><strong>update</strong></p>

<p>Since the money finally arrived, I guess i could slightly rewrite the question such as:</p>

<p>How can there be such a (long) latency from the moment a transaction is executed (eg. I get a transaction hash) to the moment the transaction is seen on the system (eg. blockchain.info)? </p>

<p>how can it be that it is not showing (hours later, not seconds later)?</p>

<p>How can I know the hash I got is valid/real?</p>
 153: <p>Your account at Bitcoin-Central is a hosted (shared) E-Wallet.</p>

<p>This means that you are not withdrawing your bitcoins, you are sending a request to the E-Wallet provider to withdraw your bitcoins.  </p>

<p>If for whatever reason that E-Wallet provider is unable to service that request immediately (for example, their hot wallet is depleted and they need to wait until business hours to get access to the bank vault to be able reload from cold storage) then the site might provide to you confirmation of your withdrawal request but that doesn't mean a Bitcoin transaction was broadcast to the network.</p>

<p>If you have a transaction hash, and that transaction is broadcast, then you should see it on Blockchain.info. </p>

<p>Otherwise, the problem is with the E-Wallet provider.</p>
