How to position elements next to each other in CSS without using float. i.e. main content next to sidebar

I have a sidebar. I have main content. I want to position my main content div next to my left side bar. My main content div is in the form of a CSS-grid layout. I determined the grid will be best to contain the information I need to display, depicted by a mock-up I was given. I was exploring the option of making the entire HTML page a grid, but I am unsure how to tackle this. So, I figured I will make create a div for my side bar and make it stay there while my main content, the grid, will move around that. But to no avail.

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Grid</title>
  <link rel="stylesheet" type="text/css" href="styles/normalize.css">
  <link rel="stylesheet" type="text/css" href="scratch.css">
</head> 
  <style>
    body {
      background: darkgrey;
      height: 1000px;
      position: relative;
    }

    .side-bar {
      background: red;
      padding: 0;
      margin: 0;
      width: 202px;
      height: 100%;
      position: relative;
    }

    .side-bar p{
      padding: 0;
      margin: 0;

    }

    .grid-container {
      display: grid;
      background: #E1E1E1;
      height: 500px;
      width: 1100px;
      grid-template-columns: 250px 250px 250px 250px;
      grid-template-rows: 200px 200px;
      grid-gap: 30px 20px;
      padding: 0;
      margin: 0 25px 0 30px;
      justify-content: right;
      align-content: center;
      position: relative;
      left: 400px;
    }

    .grid-items {
      font-weight: bold;
    }

    .grid-item1 {
      background: greenyellow;
    }

    .grid-item2 {
      background: rosybrown;
    }

    .grid-item3 {
      background: cadetblue;
    }

    .grid-item4 {
      background: darkturquoise;
    }

    .grid-item5 {
      background: darkkhaki;
      grid-column: span 2;
    }

    .grid-item6 {
      background: lightblue;
      grid-column: span 2;
    }
  </style>
  <body>

    <div class="side-bar">
      <p>Side Bar</p>
    </div>

    <div class="grid-container">
      <div class="grid-items grid-item1">
        <p>Grid Item 1</p>
      </div>

      <div class="grid-items grid-item2">
        <p>Grid Item 2</p>
      </div>

      <div class="grid-items grid-item3">
        <p>Grid Item 3</p>
      </div>

      <div class="grid-items grid-item4">
        <p>Grid Item 4</p>
      </div>

      <div class="grid-items grid-item5">
        <p>Grid Item 5</p>
      </div>

      <div class="grid-items grid-item6">
        <p>Grid Item 6</p>
      </div>
    </div>
  </body>
</html>

Solution

Your best bet is to have a main grid that contains the sidebar and a grid inside it that contains the main content:

body,
html {
  background: darkgrey;
  height: 100%;
  margin: 0;
}

#horizontal-menu {
  background: lightblue;
  padding: 8px;
  margin-bottom: 15px;
}

#horizontal-menu p {
  margin: 0;
}

.grid-container {
  display: grid;
  grid-template-columns: 1fr 2fr 1fr;
  grid-gap: 15px;
  height: 100%;
}

.side-bar {
  background: red;
  padding: 0;
  margin: 0;
  height: 100%;
  grid-column: 1 / 2;
}

.grid-items-container {
  grid-column: 2 / 3;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-template-rows: repeat(2, 1fr);
  grid-gap: 30px 20px;
  background: #E1E1E1;
  padding: 15px;
}

.side-bar p {
  padding: 0;
  margin: 0;
}

.grid-items {
  font-weight: bold;
}

.grid-item1 {
  background: greenyellow;
}

.grid-item2 {
  background: rosybrown;
}

.grid-item3 {
  background: cadetblue;
}

.grid-item4 {
  background: darkturquoise;
}

.grid-item5 {
  background: darkkhaki;
  grid-column: span 2;
}

.grid-item6 {
  background: lightblue;
  grid-column: span 2;
}

<div id="horizontal-menu">
  <p>Menu</p>
</div>

<div class="grid-container">

  <div class="side-bar">
    <p>Side Bar</p>
  </div>

  <div class="grid-items-container">

    <div class="grid-items grid-item1">
      <p>Grid Item 1</p>
    </div>

    <div class="grid-items grid-item2">
      <p>Grid Item 2</p>
    </div>

    <div class="grid-items grid-item3">
      <p>Grid Item 3</p>
    </div>

    <div class="grid-items grid-item4">
      <p>Grid Item 4</p>
    </div>

    <div class="grid-items grid-item5">
      <p>Grid Item 5</p>
    </div>

    <div class="grid-items grid-item6">
      <p>Grid Item 6</p>
    </div>
  </div>
</div>