Pure JS Add Styles
HTML
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JavaScript
var css = '*{background:#444 !important;color:lightgrey !important;}',
head = document.head || document.getElementsByTagName('head')[0],
style = document.createElement('style');
style.type = 'text/css';
if (style.styleSheet) {
style.styleSheet.cssText = css;
} else {
style.appendChild(document.createTextNode(css));
}
head.appendChild(style);