My ripples are totally missing and my wallet is now 0. What happen to them???
Did the client log you out? It loses it's balance information when it does (until it gets re-logged in, not permanently).
The webclient uses websockets to talk to the ripple servers and occasionally that connection gets reset and it can take the client a few seconds before it gets a new connection.
Anyway, your account currently has exactly 300 XRP.