Web Typography at Scale CSS - Original resource: http://typecast.com/blog/a-more-modern-scale-for-web-typography

typography-scale.css

body {
    font-size: 100%;
}

body,
caption,
th,
td,
input,
textarea,
select,
option,
legend,
fieldset,
h1,
h2,
h3,
h4,
h5,
h6,
.h1,
.h2,
.h3,
.h4,
.h5,
.h6 {
    font-size-adjust: 0.5;
}

body {
    font-size: 1em;
    /* equivalent to 16px */
    line-height: 1.25;
    /* equivalent to 20px */
}

@media (min-width: 43.75em) {
    body {
        font-size: 1em;
        /* equivalent to 16px */
        line-height: 1.375;
        /* equivalent to 22px */
    }
}

h1,
.h1 {
    font-size: 2em;
    /* 2x body copy size = 32px */
    line-height: 1.25;
    /* 45px / 36px */
}

@media (min-width: 43.75em) {

    h1,
    .h1 {
        font-size: 2.5em;
        /* 2.5x body copy size = 40px */
        line-height: 1.125;
    }
}

@media (min-width: 56.25em) {

    h1,
    .h1 {
        font-size: 3em;
        /* 3x body copy size = 48px */
        line-height: 1.05;
        /* keep to a multiple of the 20px line height and something more appropriate for display headings */
    }
}

h2,
.h2 {
    font-size: 1.625em;
    /* 1.625x body copy size = 26px */
    line-height: 1.15384615;
    /* 30px / 26px */
}

@media (min-width: 43.75em) {

    h2,
    .h2 {
        font-size: 2em;
        /* 2x body copy size = 32px */
        line-height: 1.25;
    }
}

@media (min-width: 56.25em) {

    h2,
    .h2 {
        font-size: 2.25em;
        /* 2.25x body copy size = 36px */
        line-height: 1.25;
    }
}

h3,
.h3 {
    font-size: 1.375em;
    /* 1.375x body copy size = 22px */
    line-height: 1.13636364;
    /* 25px / 22px */
}

@media (min-width: 43.75em) {

    h3,
    .h3 {
        font-size: 1.5em;
        /* 1.5x body copy size = 24px */
        line-height: 1.25;
    }
}

@media (min-width: 56.25em) {

    h3,
    .h3 {
        font-size: 1.75em;
        /* 1.75x body copy size = 28px */
        line-height: 1.25;
    }
}

h4,
.h4 {
    font-size: 1.125em;
    /* 1.125x body copy size = 18px */
    line-height: 1.11111111;
}

@media (min-width: 43.75em) {

    h4,
    .h4 {
        line-height: 1.22222222;
        /* (22px / 18px */
    }
}

blockquote {
    font-size: 1.25em;
    /* 20px / 16px */
    line-height: 1.25;
    /* 25px / 20px */
}

@media (min-width: 43.75em) {
    blockquote {
        font-size: 1.5em;
        /* 24px / 16px = */
        line-height: 1.45833333;
        /* 35px / 24px */
    }
}