((Sorry, Web is radius 20, so the target is 15 feet behind them, reflex 17 or be grappled. Afterward they need to make a combat maneuvers check or Escape artist check DC 17 to escape. Web is difficult terrain and provides cover if there is 1 square of web between targets not counting the square they are in, or total cover if there is 4 squares of web between the target and attacker. Web is highly flammable, and targets take extra damage if they take fire damage in the web. More info here: http://www.d20pfsrd.com/magic/all-spells/w/web (http://www.d20pfsrd.com/magic/all-spells/w/web) ))