In the example below, when I click the button, it says \"Load was performed\" but no text is shown.
I have a clientaccesspolicy.xml
I don't think any browser obeys clientaccesspolicy.xml or crossdomain.xml for XMLHttpRequest.
clientaccesspolicy.xml
crossdomain.xml
There are other mechanisms you can look at, such as Cross-Origin Resource Sharing. This is supported by Firefox 3.5 and later.