Why do spiders shake if you touch their web?

Afshan Ali's answer is correct, and the species of spider this is most noted in usually goes by the name “Cellar Dweller. read more

You are propably asking about the long legged spiders.The shaking is known as whirling.Experts beleive thet they do it to make the predator(according to the spider you are trying to eat them) confuse about their body. read more

Others you can’t even tell like the paper wasps who put an invisible chemical on the stalk of their nest which repels ants from raiding the larval cells for food. Orb spiders are intriguing because of their huge and sometimes ornate webs. read more