关于跨域的ajax

$.getJSON("http://query.yahooapis.com/v1/public/yql?callback=?", {   
				    q: "select * from json where url='http://baidu.kuaidi100.com/query?type=tiantian&postid=886511927358&id=4'",   
				    format: "json"   
				}, function(data) {   
				    var $content = $("#content")   
				    if (data.query.results) {  
				        var result = JSON.stringify(data.query.results);
				        alert(result);
				        $content.text(result);  
				        var obj = eval('('+result+')');
				        alert(obj.json.message);
				    }  
				});