Actually, browsers often implement features that aren't in a standard, just because they think it's a good idea. Some of those end up being memorialized by the

Actually, browsers often implement features that aren't in a standard, just because they think it's a good idea. Some of those end up being memorialized by the W3C and part of HTML. Many of the features of HTML5 started that way, including, in this case, web fonts (part of CSS3).