the best way to differentiate characters for IE6,7,8 and Firefox

different-characters-for-firefox.css

@-moz-document url-prefix() {
  // only firefox
}

differntiate-characters-for-ie678.css

* html p {        /* IE6 exclusively */
  color: blue;
}
* + html p {      /* IE7 exclusively */
  color: pink;
}
p {
  color: red;     /* all browsers */  
  color: green\9; /* IE8 and below */  
  *color: yellow; /* IE7 and below */  
  _color: orange; /* IE6 exclusively */  
}