redmineforumsidebarremover.user.js

// ==UserScript==
// @name           Redmine forum Sidebar remover
// @namespace      http://redmine.org
// @description    Makes the content area of the redmine forums full-width
// @include        http://www.redmine.org/projects/redmine/boards/*
// @include        http://www.redmine.org/projects/redmine/boards
// @include        http://www.redmine.org/boards/*
// ==/UserScript==
// I use Adblock Plus along with this - if you don't block the giant sidebar advert things might look a little wonky

var css = new Array();

function writeStyle(css) {
    var style = document.createElement('style');
    style.type = 'text/css';
    if (document.getElementsByTagName) {
        document.getElementsByTagName('head')[0].appendChild(style);
        if (style.sheet && style.sheet.insertRule) {
            for (var i = 0; i < css.length; i++) {
                style.sheet.insertRule(css[i], 0);
            }
        }
    }
}

function addStyle(style) {
    css[css.length] = style;
}

addStyle("#content { width: 98%; }");

writeStyle(css);