【mouse】
<!DOCTYPE html>
<html>
<head>
<script type='text/javascript'>
function show() {
document.getElementById('cat').style.display = "block";
}
function hide() {
document.getElementById('cat').style.display = "none";
}
</script>
</head>
<body>
<a href='#' onmouseover='show();' onmouseout='hide();'>hover</a>
<div id='cat' style='display: none;'>cat</div>
</body>
</html>
