Question

I’m curious what something like this means in CSS:

background-color: #080808 \9;

I know the hex color notation, of course, but I’ve never seen \9 used before. Even looking at the w3c, I’m not sure they define it either: color units

Answer 1

That’s an old Internet Explorer hack

\9 hack WORKS for: IE8 IE8 Standards, IE8 IE7 Standards, IE8 Quirks mode, IE7 Quirks, IE7 Standards (all varieties of IE8), IE6

So, in short, if you want an IE CSS hack that works in all flavors of IE, use the backslash-nine hack.

source