CSS3 Click Chart | CSS3 Browser Support and Information

Rem Units

Allows you to define a root em unit value on the html element, then use values on subsequent elements that are relative to the specified root unit.

html {
    font-size: 20px;
}

    p {
        font-size: 1.5rem;	
    }

For a live demonstration of CSS3 rem units, visit this link in a supporting browser.

IE9+, Firefox 3.6+, Chrome 4+, Safari 5+, Opera 11.6+