Even if it's not recommended, it is sometimes required to specify CSS settings to specific browsers only. Here's how to do it for Internet Explorer:
.node {
background: gray; /* standard */
background: yellow\0; /* IE 11 and below */
background: pink\9; /* IE 8 and below */
*background: green; /* IE 7 and below */
_background: blue; /* IE 6 */
}Currently Firefox and Chrome browsers do recognize these CSS values as invalid and therefore don't use them.
Sources: