Code Review: Dasmoto's Arts & Crafts

Hello, this is Triston.

I am looking to improve my code for this project. I noticed in the activity page that the result on the sidebar has a minimum width of 612 pixels. As a result, I added code in my CSS to match the page.

CSS:

* {
  font-family: Helvetica, sans-serif;
}

header {
  width: 100%;
  margin: 40px auto;
  background-image: url("https://content.codecademy.com/courses/freelance-1/unit-2/pattern.jpeg");
  min-width: 612px;
}

h1 {
  font-size: 100px;
  font-weight: bold;
  color: khaki;
  text-align: center;
}

.headerbox h2 {
  font-size: 32px;
  font-weight: bold;
  color: white;
}

main {
  min-width: 612px;
}

#brushes {
  background-color: mediumspringgreen;
}

#frames {
  background-color: lightcoral;
}

#paint {
  background-color: skyblue;
}

strong {
  color: blue;
}

HTML:

<!DOCTYPE html>

<html>
  <head>
    <meta charset="utf-8" />
    <title>Dasmoto's Arts & Crafts</title>
    <link rel="stylesheet" type="text/css" href="index.css">
  </head>
  <body>
    <!-- Header -->
    <header>
      <h1>Dasmoto's Arts & Crafts</h1>
    </header>
    <!-- Main -->
    <main>
      <!-- Sections are used to demarcate listings. They each contain a "headerbox" div and an article element. -->
      <section>
        <div class="headerbox" id="brushes">
          <h2>Brushes</h2>
        </div>
        <article>
          <img src="https://content.codecademy.com/courses/freelance-1/unit-2/hacksaw.jpeg" />
          <h3>Hacksaw Brushes</h3>
          <p>Made of the highest quality oak, Hacksaw brushes are known for their weight and ability to hold paint in large amounts. Available in different sizes. <strong>Starting at $3.00 / brush.</strong></p>
        </article>
      </section>
      <!-- section 2 of page -->
      <section>
        <div class="headerbox" id="frames">
          <h2>Frames</h2>
        </div>
        <article>
          <img src="https://content.codecademy.com/courses/freelance-1/unit-2/frames.jpeg" />
          <h3>Art Frames (assorted)</h3>
          <p>Assorted frames made of different material, including MDF, birchwood, and PDE. Select frames can be sanded and painted according to your needs. <strong>Starting at $2.00 / frame.</strong></p>
        </article>
      </section>
      <!-- section 3 of page -->
      <section>
        <div class="headerbox" id="paint">
          <h2>Paint</h2>
        </div>
        <article>
          <img src="https://content.codecademy.com/courses/freelance-1/unit-2/finnish.jpeg" />
          <h3>Clear Finnish Paint</h3>
          <p>Imported paint from Finland. Over 256 colors available in-store, varying in quantity (1 oz. to 8 oz.). Clean Finnish paint microbinds to canvas, increasing the finish and longevity of any artwork. <strong>Starting at $5.00 / tube.</strong></p>
        </article>
      </section>
    </main>
  </body>
</html>

I am looking for a way to make the process of applying a global minimum width more efficient. Does anyone have any ideas on how to accomplish this task?

Thanks,
Triston