CSS Hacks

2

body:empty {
    background: blue;
}

Firefox

body {
    background: red;
}
    @-moz-document url-prefix() {
    body {
        background: blue;
    }
}

Google Chrome

/*
The following hack will target both Safari 3 and Google Chrome.
*/

body {
    background: red;
}
    @media screen and (-webkit-min-device-pixel-ratio:0) {
    body {
        background: blue;
    }
}

Internet Explorer

/*
By placing a pound(#) symbol at the beginning of a CSS property, 
it will be ignored by all browsers except Internet Explorer. 
This works as a general hack that will cover all versions of IE.
*/

body {
    background: red;
    #background: blue;
}

Internet Explorer 6

/*
An underscore(_) at the beginning of a CSS property works just 
like the pound(#) symbol with the exception that it will target IE6 only.
*/

body {
    background: red;
    _background: blue;
}

Internet Explorer 7

/*
An asterisk(*) works just like the underscore with the exception 
that it is only read in Internet Explorer 7.
*/

html > body {
    background: red;
    *background: blue;
}

Revised Not tested

* html h1 {} targets IE 6
  html > body h1 {} targets IE 7 and later
  h1 {*property:value;} targets IE 7 and below
  html > body h1 {*property:value;} targets IE 7 only

Safari 2

/*
Placing a pound(#) symbol at the end of a CSS property group will 
cause all properties within that group and anything after the 
pound symbol to be ignored. This does NOT work in Safari 3.
*/

body {
    background: blue;
}
body {
    background: red;
#
}
h1 {
    /* This style will also be ignored by Safari 2 */
}