Tim Cook answered
It is difficult to know for certain, but the spider you have described sounds like a female writing spider, also know as the black and yellow spider.
There Is No Need to Panic!
Writing spiders are not poisonous, although they will bite if agitated. Therefore, there is no need to set about removing it from your home. Their diet consists of flying insects, and a female writing spider can take down an insect twice her size. Writing spiders also have distinctive webs, around two foot across, circular and of a dense, zig-zag construction. Tall vegetation or the underside of window frames seem to be its preferred spots to make its home. Here's a film of a writing spider capturing its prey: