W3School TIY
编辑您的代码：
<!DOCTYPE html> <html> <head> <style> div { width:100px; height:100px; background:blue; transition-property:width; transition-duration:5s; transition-delay:2s; /* Firefox 4 */ -moz-transition-property:width; -moz-transition-duration:5s; -moz-transition-delay:2s; /* Safari and Chrome */ -webkit-transition-property:width; -webkit-transition-duration:5s; -webkit-transition-delay:2s; /* Opera */ -o-transition-property:width; -o-transition-duration:5s; -o-transition-delay:2s; } div:hover { width:300px; } </style> </head> <body> <div></div> <p>请把鼠标指针移动到蓝色的 div 元素上，就可以看到过渡效果。</p> <p><b>注释：</b>过渡效果会在开始前等待两秒钟。</p> <p><b>注释：</b>本例在 Internet Explorer 中无效。</p> </body> </html>
查看结果: