I have withdrawn bitcoins from my account in MtGox to my Multibit installed in my computer. Several hours after BTC are not in MtGox and neither in my account. I have verified the address and it is right. I can see the direction of the address in blockchain but it appears "transactions:0". Is this normal?
Even without the transaction hash, you can still use these websites to try and find it by looking for the Bitcoin address you have withdrawn to. You may wish to check your MtGox account history to see which Bitcoin address they sent your Bitcoin.
If you do not see the transaction, don't panic. Especially if you have not included a transaction fee, miners may be slow to incorporate it into any block, in which case these websites will not find the transaction in any block, and might indeed not have seen the transaction at all.