title: Absolute URLs omitting the protocol (scheme) in order to preserve the one of the current page
body: <p>I saw the <code>//somepage.com/resource</code> url format. For example:</p>
  
  <pre><code>&lt;img src="//remotesite.com/image1.jpg" /&gt;
  </code></pre>
  
  <p>The point of this is that if the current page (the page defining the <code>img</code> tag) is using <code>http</code>, then the request to the remote site is made via http. If it is https - it's https. This eliminates browser warnings of not fully encrypted pages.</p>
  
  <p>My question is - is this URL format safe to use for all browsers. And is it a standard?</p>