This greasemonkey script displays as discarded InfoJobs.net' offers that user is not interested anymore. It also adds a button of "Discard" next to the button of "Inscribe".

DiscardedInfojobsOffers.user.js

// ==UserScript==
// @description Display as discarded InfoJobs.net' offers that user is not interested anymore.
// @description Add a button of "Discard" next to the button of "Inscribe".
// @include https://www.infojobs.net/*
// @name Discarded Infojobs' Offers
// @name:es-MX Ofertas de InfoJobs Descartadas
// @downloadURL https://gist.github.com/Silverium/c443b8fb77a7f51b3c71
// @updateURL https://gist.github.com/Silverium/c443b8fb77a7f51b3c71
// @namespace github.com/Silverium
// @author Soldeplata Saketos Candela
// @version 1
// @releasedOn 24/06/2015
// @grant none
// ==/UserScript==

//Data control. Only if elements exist, do the code
if (document.getElementById('candidate_application')) {
    function discardJobs() {
        //First, select the inscription button by ID
        var applyForJobButton = document.getElementById('candidate_application');
        applyForJobButton.innerHTML = "Inscribirme!"; //Shortening the text
        //Then add the custom button
        var btn = document.createElement("A"); // Create an <a> element
        btn.setAttribute("class", "btn btn-primary btn-medium pull-right"); // set button styling with twitter's bootstrap
        btn.setAttribute("onclick", "javascript:launchBack(this);return false;"); //go back to previous index
        btn.style.background = "darkred"; //change background color
        //animating mouse over :)
        btn.onmouseenter = function() {
            mouseEnter()
        };
        function mouseEnter() {
            btn.style.background = "black";
        }
        btn.onmouseleave = function() {
            mouseLeave()
        };
        function mouseLeave() {
            btn.style.background = "darkred";
        }
        var t = document.createTextNode("DESCARTAR"); // Create a text node
        btn.appendChild(t); // Append the text to <a> button
        applyForJobButton.parentNode.appendChild(btn); // Append <button> to "Inscribirme a esta oferta" button
    }
    discardJobs();
}

//customize results by color:

if (document.getElementsByClassName("disabled")) { //do they exist? => do the code
    function customizeGreen() {
        //Already inscribed will be lightgreen
        var checked = document.getElementsByClassName("disabled");
        for (i = 0; i < checked.length; i++) {
            checked[i].style.backgroundColor = "lightgreen";
        }
    }
    customizeGreen();
}
if (document.getElementsByClassName("result-list-title")) { //do they exist? => do the code
    function customizeRed() {
        var titleHeader = document.getElementsByClassName("result-list-title");
        for (j = 0; j < titleHeader.length; j++) {
            if (titleHeader[j].tagName == "H2") {
                var offerCont = document.createElement("A"); // Create an <a> element
                var hijos = titleHeader[j].parentNode.childNodes; //set all elements inside the container as an array to move them

                titleHeader[j].parentNode.appendChild(offerCont); //insert the <a> element into the container

                var urlRef = titleHeader[j].childNodes[1].getAttribute("href"); //get the href value to later pass it to offerCont

                offerCont.setAttribute("href", urlRef); //pass the href of the <a> element
                offerCont.setAttribute("class", "redCustomized"); //insert custom class

                while (hijos.length > 1) {
                    offerCont.appendChild(hijos[0]); //move all elements inside the <a> element
                }
            }   
        }
    }
    var estilo = document.createElement("STYLE"); //Create a <style> element
    document.getElementById("ca").appendChild(estilo); //insert the stylesheet element
    estilo.innerHTML = ".redCustomized  a:visited{color: lightsalmon}"; //style with color visited links and custom class
    customizeRed();
}