Usability. Speech. CSS - Conditional comments. Page last changed today Conditional comments only work in IE, and are thus excellently suited to give special instructions meant only for IE.
They are supported from IE 5 up until IE9 (inclusive). Older IE versions frequently need some extra CSS in order to show your pages right. Conditional comments are the best way to add this CSS, since the system is explicitly designed for this use case. If you need special styles for IE10 or up you’ll have to find another method, since conditional comments were disabled in IE10.