Deprecate protocol-relative URLs

Always use the HTTPS URL when it’s available.

See also:
* https://github.com/konklone/cdns-to-https#conclusion-cdns-should-redirect-to-https
* http://www.paulirish.com/2010/the-protocol-relative-url/

Fix #1663
Close #1694

dist/doc/html.md

@@ -145,8 +145,8 @@ using some polyfill CDN service, like [cdn.polyfill.io](https://cdn.polyfill.io/
 just put it before the other scripts in the bottom of the page:
 
 ```html
-    <script src="//cdn.polyfill.io/v1/polyfill.min.js"></script>
-    <script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
+    <script src="https://cdn.polyfill.io/v1/polyfill.min.js"></script>
+    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
     <script>window.jQuery || document.write('<script src="js/vendor/jquery-1.11.2.min.js"><\/script>')</script>
     <script src="js/plugins.js"></script>
     <script src="js/main.js"></script>

dist/index.html

@@ -22,7 +22,7 @@
         <!-- Add your site or application content here -->
         <p>Hello world! This is HTML5 Boilerplate.</p>
 
-        <script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
+        <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
         <script>window.jQuery || document.write('<script src="js/vendor/jquery-1.11.2.min.js"><\/script>')</script>
         <script src="js/plugins.js"></script>
         <script src="js/main.js"></script>

src/doc/extend.md

@@ -87,7 +87,7 @@ your site, for example) then you can queue up a domain name to be prefetched.
 
 ```html
 <link rel="dns-prefetch" href="//example.com">
-<link rel="dns-prefetch" href="//ajax.googleapis.com">
+<link rel="dns-prefetch" href="https://ajax.googleapis.com">
 ```
 
 You can use as many of these as you need, but it's best if they are all
@@ -107,7 +107,7 @@ Amazon S3:
 Google APIs:
 
 ```html
-<link rel="dns-prefetch" href="//ajax.googleapis.com">
+<link rel="dns-prefetch" href="https://ajax.googleapis.com">
 ```
 
 Microsoft Ajax Content Delivery Network:

src/doc/faq.md

@@ -3,8 +3,6 @@ table of contents](TOC.md)
 
 # Frequently asked questions
 
-* [Why is the URL for jQuery without
-  `http`?](#why-is-the-url-for-jquery-without-http)
 * [Why don't you automatically load the latest version of jQuery from the Google
   CDN?](#why-dont-you-automatically-load-the-latest-version-of-jquery-from-the-google-cdn)
 * [Why is the Google Analytics code at the bottom? Google recommends it be
@@ -18,35 +16,6 @@ table of contents](TOC.md)
 
 --
 
-### Why is the URL for jQuery without `http`?
-
-It is because of the use of [protocol-relative
-URLs](http://paulirish.com/2010/the-protocol-relative-url/).
-
-**N.B.** If you try to view the local web page directly in the browser, the
-browser will fail to load the assets specified using protocol-relative URLs
-as it will attempt to fetch them from the local file system. We recommend you
-use a local HTTP server to test your web pages, or a file hosting service that
-allows you to preview your web pages online (e.g.
-[Dropbox](https://www.dropbox.com/)).
-
-Setting up a local HTTP server can be done using there various
-[one-liners](https://gist.github.com/willurd/5720255):
-
-* PHP 5.4.0+ by running
-  [`php -S localhost:8080`](https://php.net/manual/en/features.commandline.webserver.php)
-  from your local directory
-* Python 2.x by running `python -m SimpleHTTPServer` from your local directory
-* Python 3.x by running `python -m http.server` from your local directory
-* Ruby 1.9.2+ by running `ruby -run -ehttpd . -p8080` from your local directory
-* Node.js by installing and running either
-  [`static -p 8080`](https://www.npmjs.org/package/node-static)
-  or [`http-server -p 8080`](https://www.npmjs.org/package/http-server)
-
-A list of more complex HTTP servers can be found
-[here](misc.md#servers-and-stacks).
-
-
 ### Why don't you automatically load the latest version of jQuery from the Google CDN?
 
 The [file](https://ajax.googleapis.com/ajax/libs/jquery/1/jquery.js) to which

src/doc/html.md

@@ -145,8 +145,8 @@ using some polyfill CDN service, like [cdn.polyfill.io](https://cdn.polyfill.io/
 just put it before the other scripts in the bottom of the page:
 
 ```html
-    <script src="//cdn.polyfill.io/v1/polyfill.min.js"></script>
-    <script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
+    <script src="https://cdn.polyfill.io/v1/polyfill.min.js"></script>
+    <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
     <script>window.jQuery || document.write('<script src="js/vendor/jquery-1.11.2.min.js"><\/script>')</script>
     <script src="js/plugins.js"></script>
     <script src="js/main.js"></script>

src/index.html

@@ -22,7 +22,7 @@
         <!-- Add your site or application content here -->
         <p>Hello world! This is HTML5 Boilerplate.</p>
 
-        <script src="//ajax.googleapis.com/ajax/libs/jquery/{{JQUERY_VERSION}}/jquery.min.js"></script>
+        <script src="https://ajax.googleapis.com/ajax/libs/jquery/{{JQUERY_VERSION}}/jquery.min.js"></script>
         <script>window.jQuery || document.write('<script src="js/vendor/jquery-{{JQUERY_VERSION}}.min.js"><\/script>')</script>
         <script src="js/plugins.js"></script>
         <script src="js/main.js"></script>