useful.user.js

// ==UserScript==
// @name           useful
// @namespace      http://www.hatena.ne.jp/hitode909/
// @description    useful
// @include        http://twitter.com/*
// @require http://code.jquery.com/jquery-latest.js
// ==/UserScript==

(function(){
     GM_registerMenuCommand('useful - clear cache', function () {
                                GM_setValue('read_posts', '{}');
                                $('li.status').show('slow');
                            });
     
     var read_posts = eval(GM_getValue('read_posts'));
     if (typeof(read_posts) == 'undefined'){
         read_posts = {};
     }
     var posts = $('li.status');
     console.log(posts.length);
     // 前に消したやつを消す
     for (var k in read_posts) if (read_posts.hasOwnProperty(k)) {
         $('li.status#'+k).hide();
     }
     
     // 消す
     var setvalue = function(v){GM_setValue('read_posts',v)};
     posts.mouseover(
         function(){
             $(this).hide('fast');
             read_posts[this.id] = true;
             setvalue(uneval(read_posts));
         }
     );
                         
 }());