Tonvid.com uses the Youtube API but Google imposes limitations to the use of their API. Every request to the API consumes some "units". They had a limit of 5 million units per day. Tonvid.com used about 3 million. Now it seems that Google lowered the limit to just 1 million. When the limit is reached the page stops working (you'll see an error message).
I'm afraid with this limit is going to be very complicated to continue with the site.