title: How do I find the smaller width of two values with different units in CSS?
body: <p>I'm trying to make a website where the maximum width is 500px, but if the window size is smaller (e.g. the user is on mobile, etc.), I want the width to just be 90%. How do I make it find the smaller value between 500px and 90%? This is what I've tried:</p>
  <pre class="lang-css prettyprint-override"><code>element {
    width: 90%, 500px;
  }
  </code></pre>
  <p>What am I doing wrong?</p>