hover (:hover)
The :hover CSS pseudo-class matches when the user designates an element with a pointing device, but does not necessarily activate it. This style may be overridden by any other link-related pseudo-classes, that is :link, :visited, and :active, appearing in subsequent rules. In order to style appropriately links, you need to put the :hover rule after the :link and :visited rules but before the :active one, as defined by the LVHA-order: :link — :visited — :hover — :active.
Visual user agents, like Firefox, Internet Explorer, Safari, Opera or Chrome, apply the associated style when the cursor (mouse pointer) hovers over an element.
Example
<!DOCTYPE html>
<html>
<head>
<style>
a:hover {
background-color: #F60;
color: #FFF;
}
</style>
</head>
<body>
<a href="#">Hover Mouse Here</a>
</body>
</html>
