Here is the simple example of YUI ajax with Post and Get method:

POST request:

      var callback = {
                   success: function(o){
                        alert(o.responseText);
                    },
                    failure: function(o){
                        alert('Unable to connect to server.');
                    },
                    cache: false
                }
        var url = 'my_url?id=1';
        YAHOO.util.Connect.asyncRequest('POST', url, callback);

GET request

var callback = {
                   success: function(o){
                        alert(o.responseText);
                    },
                    failure: function(o){
                        alert('Unable to connect to server.');
                    },
                    cache: false
                }
        var url = 'my_url?id=1';
        YAHOO.util.Connect.asyncRequest('GET', url, callback);

Please include YUI library also.