Cross-window communicationThe “Same Origin” (same site) policy limits access of windows and frames to each other. The idea is that if a user has two pages open: one from john-smith.com, and another one is gmail.com, then they wouldn’t want a script from john-smith.com to read our mail from gmail.com. So, the purpose of the “Same Origin” policy is to protect users from information theft. Same OriginTwo URLs are said to have
