What spiders are poisonous?

Only a few species are seriously poisonous to humans.

There are these few Spiders:

black widow, African brown spider, bird spider, and if you ever see a spider with a violin shape on its back stay clear this spider can kill and is known for it.

*Edit:

The violin spider (or Brown Recluse, Loxosceles Reclusa, or Fiddleback spider) mentioned above is NOT deadly. It is difficult for doctors to diagnose spider bites, and the bite of this particular spider looks very similar to other serious conditions, so a lot of pictures/stories you see/hear about this spider being deadly are false. Though not deadly, this spider does cause very serious wounds and should be avoided. It is not aggressive.