It seems nobody bothered to answer this (this is pretty basic knowledge):

A bitcoin address is like an unbreakable deposit box. Someone has the key to it (or the key is lost). Once the coins are inside the deposit box (i.e. sent, like you did). You can ever only get them out with the key (called private key).

If that key is lost, the coins are gone forever.

So in your case, I'd try to contact the "web" (-service?) you used to host your wallet. What was the name of this service?

Was there any backup or passphrase or anything you had to store or write down that might be used to regenerate your private key?