The document discusses challenges of cross-site communication for building rich web applications and mashups due to the same-origin policy, and describes techniques currently used like server-side proxies, Flash, JSON-P, and the "JavaScript wormhole" to overcome these limitations by establishing trust relationships between domains. It also considers proposals for new cross-domain tools and the evolving browser platform to better support these use cases in the future while maintaining security.

1. Cross-Site Ajax Challenges and Techniques for Building Rich Web 2.0 Mashups Joseph Smarr Plaxo, Inc. [email_address]

6. Server-side proxy Web Page Domain A Server Domain A Server Domain B

8. Flash proxy Web Page Domain A Server Domain B Flash crossdomain.xml

10. JSON-P Web Page Domain A Server Domain B <script> JSON + callback

18. zazzle.com/email_this plaxo.com/ab_chooser plaxo.com/ab_chooser Iframe: zazzle.com/cb.html  Script: plaxo.com/ab_chooser/abc_comm.jsdyn