in your CSS stylesheets. @-moz-document { { body { color: purple; background: yellow; } } } Full run down: http://developer.mozilla.org/en/CSS/@-moz-document Only it targets all a Gecko based browsers, not just Firefox, like Seamonkey . Same format as media-queries . answered Jul 21 '11 at 22:46 palhmbs 56 ● 2 edited Jul