Origin XX is isn't allowed by access-control-allow-origin. Solution

Origin XX is isn't allowed by Access-control-allow-origin. is actually JS cross-domain access problem

What caused the problem that Ajax cannot request across domains.

Ajax itself actually interacts with the data through the XMLHttpRequest object, and the browser, for security reasons, does not allow the JS code to operate across domains, so it warns.
Solution Red is the point of the place.

    function Sel () {
        $.ajax ({  
        URL: "", 
        Type: "Get",  
        dataType: ' Jsonp ',  
        timeout:5000,  
        success: function (JSON) {
            alert (JSON);
        }, 
        error:function (XHR, ajaxoptions, thrownerror) {  alert ("Http Status: "+ Xhr.status +" "+ Xhr.statustext +" \najaxoptions: "+ ajaxoptions +" \nthrownerror: "+thrownerror +" \ n "+xhr . responsetext);   });

    }

Detailed description and other methods: http://wenku.baidu.com/view/e29f37350b4c2e3f57276386.html