The first example changes the opacity of any image link when the mouse moves over it using the "hover:" pseudo class of CSS. Note the two different properties used to specify opacity in CSS below. In IE 5.5+, the "filter" property is used (range: 0-100), and in Firefox, "-moz-opacity" (range: 0-1). Both properties are proprietary, and not formally endorsed by the W3C.

The second example demonstrates applying a border to any image link when the mouse moves over it. The last definition (".toggleborder:hover") is added to overcome a IE bug, which causes the effect to not work in that browser if not added.