title: Should I use single colons (:) or double colons (::) for before, after, first-letter and first-line pseudo-elements?
body: <p>From MDN:</p>
  
  <blockquote>
    <p>The <code>::</code> notation was introduced in CSS 3 in order to establish a
    discrimination between pseudo-classes and pseudo-elements. Browsers
    also accept the notation <code>:</code> introduced in CSS 2.</p>
  </blockquote>
  
  <p>If the notation <code>:</code> will always be accepted by CSS3 browsers, should I use it because it works on old and new browsers?</p>
  
  <p>Or should I use both of them, <code>:</code> for old browsers and <code>::</code> for new ones, because the notation <code>:</code> won't be always accepted?</p>
  
  <hr>
  
  <p><strong>Note</strong>: I think my question isn't a duplicate isn't a duplicate of <a href="https://stackoverflow.com/questions/10181729/should-i-use-single-or-double-colon-notation-for-pseudo-element-css">Should I use single or double colon notation for pseudo-elements?</a> because the other question asks about single vs double notation for ALL pseudo-elements; while my question is only about pseudo-elements defined in CSS2, not the new ones defined in CSS3, because I already know that with those I must use <code>::</code>.</p>