I am making a react app. I made a nav bar using css. In it, when I am loading the website, it is not coming to the top of the screen. There is some gap between. If you want to see my code -

```
import { Outlet, Link } from "react-router-dom";
import React from "react";
import "./layout.css";

class Layout extends React.Component {
  render() {
    return (
      <>
        <header class="header">
          <a href="" class="logo">
            INDUSTRIES
          </a>
          <input class="menu-btn" type="checkbox" id="menu-btn" />
          <label class="menu-icon" for="menu-btn">
            <span class="navicon"></span>
          </label>
          <ul class="menu">
            <li>
              <Link to="/">Home</Link>
            </li>
            <li>
              <Link to="/blogs">Text</Link>
            </li>
            <li>
              <Link to="/contact">Contact</Link>
            </li>
          </ul>
        </header>

        <Outlet />
      </>
    );
  }
}
export default Layout;

```

here is css -

```
a {
  color: #000;
}

/* header */

.header {
  background-color: #fff;
  box-shadow: 1px 1px 4px 0 rgba(0, 0, 0, 0.1);
  position: fixed;
  width: 100%;
}

.header ul {
  margin: 0;
  padding: 0;
  list-style: none;
  overflow: hidden;
  background-color: #fff;
}

.header li a {
  display: block;
  padding: 20px 20px;
  border-right: 1px solid #f4f4f4;
  text-decoration: none;
}

.header li a:hover,
.header .menu-btn:hover {
  background-color: #f4f4f4;
}

.header .logo {
  display: block;
  float: left;
  font-size: 2em;
  padding: 10px 20px;
  text-decoration: none;
}

/* menu */

.header .menu {
  clear: both;
  max-height: 0;
  transition: max-height 0.2s ease-out;
}

/* menu icon */

.header .menu-icon {
  cursor: pointer;
  display: inline-block;
  float: right;
  padding: 28px 20px;
  position: relative;
  user-select: none;
}

.header .menu-icon .navicon {
  background: #333;
  display: block;
  height: 2px;
  position: relative;
  transition: background 0.2s ease-out;
  width: 18px;
}

.header .menu-icon .navicon:before,
.header .menu-icon .navicon:after {
  background: #333;
  content: "";
  display: block;
  height: 100%;
  position: absolute;
  transition: all 0.2s ease-out;
  width: 100%;
}

.header .menu-icon .navicon:before {
  top: 5px;
}

.header .menu-icon .navicon:after {
  top: -5px;
}

/* menu btn */

.header .menu-btn {
  display: none;
}

.header .menu-btn:checked ~ .menu {
  max-height: 240px;
}

.header .menu-btn:checked ~ .menu-icon .navicon {
  background: transparent;
}

.header .menu-btn:checked ~ .menu-icon .navicon:before {
  transform: rotate(-45deg);
}

.header .menu-btn:checked ~ .menu-icon .navicon:after {
  transform: rotate(45deg);
}

.header .menu-btn:checked ~ .menu-icon:not(.steps) .navicon:before,
.header .menu-btn:checked ~ .menu-icon:not(.steps) .navicon:after {
  top: 0;
}

/* 48em = 768px */

@media (min-width: 48em) {
  .header li {
    float: left;
  }
  .header li a {
    padding: 20px 30px;
  }
  .header .menu {
    clear: none;
    float: right;
    max-height: none;
  }
  .header .menu-icon {
    display: none;
  }
}

```

Over here, there is a gap above the nav bar. Why is this coming and how to fix it ? Please help me!