title: Flex error on using HTTP Service
body: <p>Hi I'm trying a simple tutorial of retrieving RSS feeds from yahoo and keep getting this error:</p>
  
  <p>RPC Fault faultString="Security error accessing url" faultCode="Channel.Security.Error" faultDetail="Destination: DefaultHTTP"</p>
  
  <p>I've seen some articles that say I need a crossdomain.xml file, but I don't really know how to set this file up and how to use it from the Flex SDK compiler (mxmlc). </p>
  
  <p>Thanks</p>