Unfortunately WordPress is not allowing to add <style> tag to show demo so just use your senses

<div class="box">
    The box should be green in IE 5.5 and below, orange in IE 6 and red in IE 7. In every other browser it should be blue.
</div>
.box {
   background: #00f;
   *background: #f00; /*IE7 and below*/
   _background: #0f0; /*IE 6 and below*/
   _bac\kground: #f60; /* IE6 only */
   padding: 7px;
   color: #fff;
}

Source