It could be poisonous, so your best strategy would be to leave it alone.
You really need a much more detailed description or, even better, a photo, for anyone to be able to identify the spider as there are many with black and white markings.
Think how big it was, and whether it was furry? Were the dots all over the body? Were there any other distinguishing marks? It's behavior could also be relevant to identifying it.
You might have encountered a phidipus spider which are relatively common in the west of the USA. They are a type of jumping spider and there are around 60 described species.
Phidippus californicus is commonly found in the south west of the USA, especially in Arizona, New Mexico, Nevada, Texas and Utah. This particular type usually has some visible red on its body too.
Phidippus spiders are usually active from mid-morning to dusk and you're most likely to see them in bushes. They are often observed running along branches, frequently stopping to scan their surroundings.
It's retreat is a slightly flattened tube of silk, surrounded by guy-lines that attach it to the twigs or leaves of the bush.
As for whether it is venemous, Phidippus spiders do use poison on their prey after they have trapped it. But as the prey is usually wasps, flies and other small insects, only a small amount is required. They are, therefore, relatively harmless to humans.
Be warned though, the spider you saw may not be one of these. Black and white are common insect colors so don't go picking one of these up without being sure about what it is.
A spider relatively close to this description is the parson spider. Maybe that's what you saw.
I seen a black spider with a white dot on it's back, and had very long legs, what kind of spider is that?
Yes, but only found in Europe.
I don't know but ive seen one and hose suckers are HUGE!!!
No. There are no "poisonous" spiders, snakes, or any other animal for that matter. The term is "venomous". Big difference. Spiders bite to paralyze their prey, then consume it. Most spiders in north america possess a non-toxic venom to humans. The exception would be the brown recluse and black widow.
No, just a house jumping spider
Well, a black spider with a white dot is on it poison.
I cannot say if they are poisonous but they are jumping spiders and they are HUGE!!!
That's a Daring Jumping spider and it's not poisonous, but it can bite especially if handled.
Spiders are not "poisonous". They are venomous. They use this to subdue their prey. But in north america all spiders except two have non-toxic venom. The black widow and brown recluse can pose a danger to humans due to the size of their venom glands and toxicity. The good news is these spiders do not go around thinking about nothing but biting humans. They only bite when there is no other alternative.
That sounds like Phiddipus Audax, which is a type of jumping spider most commonly found in North America... I wish I could say they're harmless but if feeling threatened, they can jump up to 2 feet.. And yes they bite. If you'd like more picture or information just google it :)
It sounds like one of the jumping spiders. I don't know if it's poisonous or not
All spiders are poisonous to one extent or another, however not all are life threatening.The only ones that aren't poisonous are daddy long legs and that because technically they are not a spider.