I don't know what I'm doing wrong here

Tell us what’s happening:
Describe your issue in detail here.

  **Your code so far**

<style>
body {
  min-height: 150vh;
}
#navbar {
  position: fixed;
  top: 0 px;
  left: 0 px;
  width: 100%;
  background-color: #767676;
}
nav ul {
  margin: 0px;
  padding: 5px 0px 5px 30px;
}
nav li {
  display: inline;
  margin-right: 20px;
}
a {
  text-decoration: none;
}
</style>
<body>
<header>
  <h1>Welcome!</h1>
  <nav id="navbar">
    <ul>
      <li><a href="">Home</a></li>
      <li><a href="">Contact</a></li>
    </ul>
  </nav>
</header>
<p>I shift up when the #navbar is fixed to the browser window.</p>
</body>
  **Your browser information:**

User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/14.0.3 Safari/605.1.15

Challenge: Lock an Element to the Browser Window with Fixed Positioning

Link to the challenge:

I have done what the task is asking me to do but I’m still not passing the test. can you help me?

my problem has been solved