$. Post (" ajax/ajax. TXT ", {username: "rose"}, function (data, status) {
Alert (" data: \ n "+ data +" \ n state: "+ status); 
}, "text"); 

The above code, when I use the GET method, everything is normal, not report any errors, path there is no problem,
But when you use the POST method, prompt Status Code: 404 Not Found
O solve, do not know what reason!