Blockchain.info is the most commonly used one.
Just like others said, If you want to use an online wallet you should try using blockchain.info wallet.
The best BTC Web wallet is http://blockchain.info 
There are some others Web wallets too, but blockchain is most popular walet 
There are some others Web wallets too, but blockchain is most popular walet Anyway, to answer you question, blockchain.info is imho the best one
I think the best web wallet is blockhain.info
blockchain.info is the only one you should really use
... for committing economic suicide.
Just quoting a part of our post and leaving us neutral trust feedback and making us look guilty? Please quote our warning too and help him choose a wallet.
It will also be helpful for him (and most new people on forum) if you explain him why web wallets are not secure enough instead of quoting us and writing a four word sentence (spam?).
Thanks
Edit: So far I remember that you posted (I hope my memory isn't betraying me) in this thread saying something like this "blockchain.info is the best online wallet /sarcasm" along with an image. You were obviously being sarcastic. But I wonder why would you remove that?