Bei der englischen Schreibweise herrscht bunte Vielfalt (spiderweb, spider's web, spider web):
The Macquarie Dictionary:
spider web
noun 1. Also, spider's web. a web spun by a spider, used to catch insects.
2. the fine silken thread produced by spiders.
3. something resembling a spider web: a spider web of red marks. Also, spider-web, spiderweb
Canadian Oxford Dictionary:
spiderweb n. 1. a web spun by a spider. 2. something resembling this
Random House Webster's Unabridged:
spider web, the web that is spun by a spider, made of interlaced threads of viscous fluid that harden on exposure to air. Also, spider's web.
http://encarta.msn.com/dictionary_/spiderweb.htmlspiderweb
noun
Definitions:
web spun by spider: a web that is constructed by a spider to entrap prey, using silk produced from fluid from its abdominal glands