There are several interesting style on Mozilla’s specific CSS. One of the most interesting trick is changing the style of the text when user highlighted the text using -moz-selection property. Look below:

[css]::-moz-selection{
background-color: #ff0000;
color: #fff;
}[/css]

now when user selected or highlighted any text, the background color will change to red (#ff0000) and the text color is white (#fff). I used that style on this site so simply highlighted any text here and see the result :))