The ESP Guitar Company

That looks to me like it could be a bridge ground wire, does this guitar have active pickups installed?

Synix is right.

Having been confirmed that it is indeed a bridge ground, here's a run down of why it's like that and what needs to be done.

1. The guitar has passive pickups
That wire should be attached to the ground at the back of the volume pot and it's come loose, reattach to pot.

2. This guitar originally shipped with passives but has had actives installed.
The wire is fine where it is. Actives don't need a bridge ground. Don't connect it.

3. The guitar shipped with actives.
It's really cool that ESP includes a bridge ground even when not needed incase the person wants to swap out for passives at a later date. Don't connect the wire, remember, actives don't need a ground.

It has actives.  You can see the battery at the right side of the photo.

It has active EMGs yes, ok so it shouldn't be wired. Yesterday I wired it to the jack but now I removed it. Thanks