Example of a correct CSS baseline

HTML

<h1>Heading Level One</h1>
<h2>Heading Level Two</h2>
<h3>Heading Level Three</h3>
<h4>Heading Level Four</h4>
<h5>Heading Level Five</h5>
<h6>Heading Level Six</h6>
<p>This is a test paragraph. This is a test paragraph. This is a test paragraph. This is a test paragraph. This is a test paragraph. This is a test paragraph. This is a test paragraph. This is a test paragraph. This is a test paragraph. This is a test paragraph. This is a test paragraph. This is a test paragraph. This is a test paragraph. This is a test paragraph. This is a test paragraph. This is a test paragraph. This is a test paragraph.</p>

CSS

html {
    background-image: -webkit-linear-gradient(hsla(0,0%,0%,0) 95%, hsla(0,25%,50%,.5) 95%);
    background-image:    -moz-linear-gradient(hsla(0,0%,0%,0) 95%, hsla(0,25%,50%,.5) 95%);
    background-image:     -ms-linear-gradient(hsla(0,0%,0%,0) 95%, hsla(0,25%,50%,.5) 95%);
    background-image:      -o-linear-gradient(hsla(0,0%,0%,0) 95%, hsla(0,25%,50%,.5) 95%);
    background-image:         linear-gradient(hsla(0,0%,0%,0) 95%, hsla(0,25%,50%,.5) 95%);
    background-position: 50% 0;
    background-size: 1.5em 1.5em;
    margin: 0;
    padding: 1.5em 3em;
}
body {
    margin: 0;
}

/* Typographic Baseline */

html {
    color: #333;
    font-family: sans-serif;
    font-size: 16px;
    line-height: 24px;
}
h1,
h2,
h3,
h4,
h5,
h6 {
    background-color: hsla(0,0%,0%,.1); /* To better illustrate */
    font-weight: bold;
    margin: 0 0 24px 0;
}
h1 {
    font-size: 48px;
    line-height: 48px;
}
h2 {
    font-size: 36px;
    line-height: 48px;
}
h3 {
    font-size: 24px;
}
h4 {
    font-size: 21px;
}
h5 {
    font-size: 18px;
}
h6 {
    font-size: 16px;
}
p {
    background-color: hsla(0,0%,0%,.1); /* To better illustrate */
    margin: 0 0 24px 0;
}