All Stack Exchange sites have a giant footer:

I don't like to have all of that space being taken up on my screen, so I built this user-style:

/**
 * Copyright © 2016 Jed Fox
 *
 * (The MIT License)
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject
 * to the following conditions:
 *
 * - The above copyright notice and this permission notice shall be
 *   included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
#footer-sites {
    display: none !important;
}

#footer #copyright, #footer #svnrev {
    display: inline-block !important;
}

#footer #svnrev::before {
    content: "//";
    margin: 0.25em;
}

^{try installing Stylish and adding this}

This shrinks the footer:

The sites are available from the Stack Exchange dropdown at the top-left, and the extra line for the revision was bothering me, so I added it to the same line.

Here is a userscript if you don’t want to use Stylish:

// ==UserScript==
// @name         Shrink the Footer
// @namespace    https://stackapps.com/questions/7091/34727
// @version      0.1
// @description  shrinks the SE footer
// @author       J F
// @license MIT
// @grant        none
// @match        *://*/*
// ==/UserScript==
var style = document.createElement('style')
style.type = 'text/css'
style.innerHTML = '#footer-sites{display:none!important}#footer #copyright,#footer #svnrev{display:inline-block!important}#footer #svnrev::before{content:"//";margin:.25em}'
document.getElementsByTagName('head')[0].appendChild(style)
$('#svnrev').appendTo($('#copyright')) // move the copyright inline

^{adapted from this answer}