title: background-image not working when used in external stylesheet,works perfectly fine when used <style> tag in html
body: <p>HTML CODE:
  (Image is present in the right directory)</p>
  
  <pre><code>    &lt;html lang="en-US"&gt;
  &lt;head&gt;
      &lt;meta charset="utf-8"&gt;
      &lt;link rel="stylesheet" href="styles/style.css"&gt;     
  &lt;/head&gt;
  &lt;body&gt;
      &lt;header&gt;
          &lt;h1&gt;Sample Header&lt;/h1&gt;
      &lt;/header&gt;
      &lt;main&gt;
          &lt;article&gt;
              &lt;h2&gt;Sample Header 2&lt;/h2&gt;
              &lt;p&gt;Sample Paragraph 1&lt;/p&gt;        
              &lt;p&gt;Sample Paragraph 2&lt;/p&gt;
          &lt;/article&gt;
      &lt;/main&gt;
  &lt;/body&gt;
  </code></pre>
  
  <p></p>
  
  <p>CSS CODE:</p>
  
  <pre><code>html{
  font-family: 'Open Sans', sans-serif;
  background-image: url('images/pattern.png');
  background-color: burlywood;
  }
  body {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  background-color: white;
  position: relative;
  }
  header {
  height: 150px;
  }
  h1 {
  font-size: 50px;
  line-height: 140px;
  margin: 0 0 0 32.5px;
  }
  main {
  background: #ccc;
  }
  article {
  padding: 20px;
  }
  h2 {
  margin-top: 0;
  }
  p {
  line-height: 2;
  }
  </code></pre>
  
  <p>background-image does not work in the above form,but when the same css-code is included in style tag,background-image works perfectly fine,why not in external stylesheet?</p>