title: Why does an attribute CSS selector work both with and without apostrophes?
body: <p>I know CSS Selectors should be generally of the following format:</p>
  <pre><code>tagName[attributeName='attributeValue']
  </code></pre>
  <p>For example <strong>Ask Question</strong> button on <a href="https://stackoverflow.com/">stackoverflow.com</a> main page is sitting inside a <code>div</code> element matching the following CSS selector <code>div[class='d-flex']</code><br />
  However I see with my Chrome DevTools that <code>div[class=d-flex]</code> locator is matching this element as well and it is found to be a correct locator!<br />
  So, my question is why the CSS selector expressions without apostrophes around the attribute values are still found as correct by the DevTools?</p>