hide_read_news.user.js

// ==UserScript==
// @name           Hide read news posts
// @namespace      http://nextdoorhacker.com/projects
// @include        http://news.ycombinator.com/
// @include        http://slashdot.org/
// @include        http://www.reddit.com/*
// @require	   http://ajax.googleapis.com/ajax/libs/jquery/1.3/jquery.min.js
// ==/UserScript==

(function() {
    // This will be executed onLoad
    // Append some text to the element with id #someText using the jQuery library.
   var location = window.location.host;
   switch(location){
    case "news.ycombinator.com":
        $("a:visited").parent().parent().each( function(){ $(this).hide();  $(this).next().hide();});
        break;
    case "slashdot.org":
        $("a.datitle:visited").parent().parent().parent().hide();
        break;
    case "www.reddit.com":
	$("a.title:visited").parent().parent().parent().hide();
	break;
    default:
        break;
   }
   
}());