Userscript forcing all websites to open links in the same tab. Useful for google, which seems to open a new tab every time you click a link.

open_in_same_tab.user.js

// ==UserScript==
// @name      Open links in same tab 
// @namespace  
// @version    1.0
// @description  Description
// @require http://code.jquery.com/jquery-latest.js
// @include        *
// ==/UserScript==

$(document).ready(function(){
    var a = document.getElementsByTagName("a"); 
    for (i=0;i<a.length;i++) { 

        if (a[i].target="_blank") { 
            a[i].target="_self" 
        } 

    }
});