<p><b>注释：</b>本例在 Internet Explorer 中无效。</p>
<!DOCTYPE html>
<html>
<head>
<style>
div
{
width:100px;
height:100px;
background:blue;
transition-property:width;
transition-duration:5s;
/* Firefox 4 */
-moz-transition-property:width;
-moz-transition-duration:5s;
/* Safari and Chrome */
-webkit-transition-property:width;
-webkit-transition-duration:5s;
/* Opera */
-o-transition-property:width;
-o-transition-duration:5s;
}
div:hover