<Please sticky this topic, it's a problem with google's servers and has been for a while>
Hello, please be assured that if you get a screen when getting on opticraft.net that looks like this:
Do not fear. This has happened on the minecraftforum also, referring an advertisement problem. I don't recall opticraft.net using advertisements so this might be Google's problem and I'll guarentee they'll fix this soon. Hang in there, there's no malware on opticraft.
Thanks, LIEKABOWSE
Edit: this is firefox's:
