title: Highlight submit button when focus on input field in html
body: <p>I am new in front-web development. I am creating a subscription form. I need to highlight the subscribe button when user clicks on the input field. How can I do it by using CSS? I don't want to use JavaScript. My HTML code is below: </p>
  
  <p>HTML: </p>
  
  <pre><code>&lt;form&gt;
       &lt;input type="text" placeholder="Your email ID"&gt;   
       &lt;input type="submit" class="submit_button" value="Subscribe"&gt;
  &lt;/form&gt;
  </code></pre>