Port twbs#20165 to v3

[skip sauce]

CONTRIBUTING.md

@@ -248,7 +248,7 @@ includes code changes) and under the terms of the
 [Adhere to the Code Guide.](http://codeguide.co/#css)
 
 - When feasible, default color palettes should comply with [WCAG color contrast guidelines](http://www.w3.org/TR/WCAG20/#visual-audio-contrast).
-- Except in rare cases, don't remove default `:focus` styles (via e.g. `outline: none;`) without providing alternative styles. See [this A11Y Project post](http://a11yproject.com/posts/never-remove-css-outlines/) for more details.
+- Except in rare cases, don't remove default `:focus` styles (via e.g. `outline: none;`) without providing alternative styles. See [this A11Y Project post](http://a11yproject.com/posts/never-remove-css-outlines) for more details.
 
 ### JS
 

docs/_includes/getting-started/accessibility.html

@@ -3,7 +3,7 @@ <h1 id="accessibility" class="page-header">Accessibility</h1>
   <p class="lead">Bootstrap follows common web standards and&mdash;with minimal extra effort&mdash;can be used to create sites that are accessible to those using <abbr title="Assistive Technology" class="initialism">AT</abbr>.</p>
 
   <h2>Skip navigation</h2>
-  <p>If your navigation contains many links and comes before the main content in the DOM, add a <code>Skip to main content</code> link before the navigation (for a simple explanation, see this <a href="http://a11yproject.com/posts/skip-nav-links/">A11Y Project article on skip navigation links</a>). Using the <code>.sr-only</code> class will visually hide the skip link, and the <code>.sr-only-focusable</code> class will ensure that the link becomes visible once focused (for sighted keyboard users).</p>
+  <p>If your navigation contains many links and comes before the main content in the DOM, add a <code>Skip to main content</code> link before the navigation (for a simple explanation, see this <a href="http://a11yproject.com/posts/skip-nav-links">A11Y Project article on skip navigation links</a>). Using the <code>.sr-only</code> class will visually hide the skip link, and the <code>.sr-only-focusable</code> class will ensure that the link becomes visible once focused (for sighted keyboard users).</p>
   <div class="bs-callout bs-callout-danger" id="callout-skiplinks">
     <p>Due to long-standing shortcomings/bugs in Chrome (see <a href="https://code.google.com/p/chromium/issues/detail?id=262171" title="Chromium bug tracker - Issue 262171: Focus should cycle from named anchor">issue 262171 in the Chromium bug tracker</a>) and Internet Explorer (see this article on <a href="http://accessibleculture.org/articles/2010/05/in-page-links/">in-page links and focus order</a>), you will need to make sure that the target of your skip link is at least programmatically focusable by adding <code>tabindex="-1"</code>.</p>
     <p>In addition, you may want to explicitly suppress a visible focus indication on the target (particularly as Chrome currently also sets focus on elements with <code>tabindex="-1"</code> when they are clicked with the mouse) with <code>#content:focus { outline: none; }</code>.</p>

less/scaffolding.less

@@ -120,7 +120,7 @@ hr {
 
 // Only display content to screen readers
 //
-// See: http://a11yproject.com/posts/how-to-hide-content/
+// See: http://a11yproject.com/posts/how-to-hide-content
 
 .sr-only {
   position: absolute;