Illustrator Tutorial: Halloween Spiders and Webs, Part 1: Spinning the Web

Open a new document in Illustrator in RGB mode, and use pixels as your unit of measurement. Set your stroke color to black and fill color to none. Select the ellipse tool in the toolbox and click once on the artboard to get the tool options. Enter 150 for height and width, and click OK to create the circle. Drag out guides from the rulers that exactly intersect the circle's center. Click the Direct Selection tool in the toolbox so you can see the anchor points and use them as a guide for the guideline placement.