When we try executing our suite on Firefox, there is an issue with the new Selenium 1.0.3 server: Got result: XHR ERROR: URL = http://www.____.com/ Response_Code = 503 Error_Message = Serrvice Temporarily Unavailable on session b882a11224b7____ This doesn't occur with the older selenium server jar but just the new one. Root Cause: This occurs mainly due to Open command If we alter the open command to have its second argument as TRUE...it works! Reference: Reference2 Also suggest that you might want to use the latest version of Selenium RC...RC's 2 and above don't throw the XHR error... Get the latest RC here .