N.B.
I've made spider webs big enough to cover a whole wall, and all I used was a ball of black yarn(you can add glitter if you want). You cut a piece about 5-6in. long, tie it in a circle, then cut 8-10 longer pieces(2 will be the distance across the web), tie them to the circle, and lay them on the floor like a wagon wheel. Start close to the center, and go around the wheel with the remaining ball, tying it to each spoke, then moving out a few inches when you complete the circle, and start again. Easy, peasy. Get a big spider at the craft store, and tie a piece of yarn to it, then tape or tack the web and spider up.