Here is the most important rule: the web wallet is not persistent, which means once you close your browser page your wallet is gone! It is short-lived and it lives only as long as the browser page is open. So in order to be able to use your account in the future or maybe copy it to CLI wallet or mobile wallet, the first thing you have to do after you create web wallet: select and copy your Private Key and store it in a safe place (for example, in password manager vault, or simply write it down in a piece of paper). Without Private Key, you won't be able to restore and use your wallet in the future!