One

background-color: #f2f2f2;
/* Sidebar */
background-color: #f7f7f7

text-color: black;

a:link { color: #1863a1 }
a:visited { color: #751590 }
a:focus { color: #0181eb }
a:hover { color: #0181eb }
a:active { color: #01579f }

#3A99D3

Highlight styles

Lorem Ipsum e-mail: background-color: gold, which is the same as Gary Johnson's e-mail campaign: #FFD700

Highlight text-shadow, from http://www.audiocheck.net/testtones_highdefinitionaudio.php:

text-shadow: -3px 0px 3px yellow, 3px 0px 3px yellow, 6px 0px 6px yellow, -6px 0px 6px yellow;

Flexbox

Animations

Twitter Bootstrap

Bootstrap themes

Ems for block widths

from Responsive enhancement

Other appealing widths:

Clearfix

Clearfix is the original method for clearfix. At SitePoint, apparently using overflow: auto also works for container elements.

Font sizes

/* Super-large top-page or mid-page heading */
font-size: 4rem; font-weight: 200;

Spacing

letter-spacing: 0.8px;

letter-spacing: .06em;

letter-spacing: 03125em;

line-height: 1.25em;

line-height: 1.09em;

line-height: 1.4375rem;

h2 { margin-bottom: 0.3em; }

CSS frameworks

Quoted file sizes are minified + gzipped.

Text colors

From oldblog.samat.org (Drupal-powered blog):

Background colors