 <p>By default the body on the page has this css:</p> <pre><code>body { display: block; margin: 8px; } body:focus { outline: none; } </code></pre> <p>at the top of your css file just add:</p> <pre><code>body { margin:0; } </code></pre> <p>this way you're working with 0 margins to begin with.</p>