that is a cobweb spider which belongs to the Theridiidae family of spiders.this one is better known as the common house spider (Achaearanea tepidariorum).if i am correct,this spider shouldn't be any longer than about 1/3" and i pretty sure that this is the type of spider it is because of the dark brown or black stripes near the tip of it.where exactly did you see this spider at?the reason i am asking is because these spiders normally dwell in dark damp places such as a basement,crawlspace,or outbuilding.word of caution though,this spider does belong to the same family as the black widow,but obviously not as dangerous as the widow of course.spiders tend to be loners,meaning that if you leave them alone and don't bother them,then they wont bother you.the ONLY spider that will make it a point to bite you is the yellow sac spider and is very commonly found in people's houses and alot of time their beds when it becomes colder.these spiders are responsible for more spider bites than any other spider in the world.they are very aggressive and will run towards you to make it a point to attack you.any other spider is more scared of you than you are of it,lol.