I used this online-wallet for a while (about 3-4 years). It was comfortable for the fast transactions and very simple. I had no troubles with security of funds (amounts were up to 0.5 btc in one time on the wallet). However, couple days ago my funds were stolen from one of the wallets on this site (0.3 btc). By the way, I had some other wallets created on this site with different secret phrase – no problem with them (amounts were smaller but also quite big, and of course after that I transferred everything on the other wallet immediately). I am sure my secret phrase was in a safety place and I used only link that I copied. I guess they are high IQ scammers who steals your crypto when you have a high balance. No worries about that. Just warned newcomers. Be safe.
Sorry for you loss but I hope you have a better wallet now to store your bitcoins. For instance a hardware wallet, see:
https://bitcointalk.org/index.php?topic=5288971.0TBH, no one should be using an obscure shoddy wallet like bitcoin-wallet anymore when we have lots of better options. Most especially storing big amounts on a hot wallet—connected to the internet, as it makes you more susceptible to online attacks which is like where most attacks happen.