This site might try to use exploit using java or flash. This exploits will run automatically without downloading.
These can be very dangerous. They can leak your identity and/or location and potentially compromise your wallets on your computer.
Nowadays it is absolutely necessary having something that prevents your browser from running java, javascript, flash and all that stuff apart for few trusted sites (no, btt is not one of them).
An antivirus is no longer enough.
The worst thing is that these malwares steal your passwords on the fly leaving no traces on your computer : after a couple of days you'll just see spam messages coming out of your mailboxes.