(19)A selection of tips
招数19：
精选技巧集合
Including height and width in <img /> tags will allow your page to render more quickly, because space can be allocated for the image before it is downloaded.
在<img />标签中包括height和width属性会加速你的页面呈现，因为下载完成之前空间可以分配给图像。
(20)Add script references at the bottom of the page, because asynchronous downloads halt when a script reference is reached. Style sheets and images can be downloaded
asynchronously.
招数20：
在页面底部添加脚本引用，因为当脚本引用到达时异步下载中断。样式表和图像是能够异步下载。
(21)Use a content delivery network (CDN) for hosting images and scripts. They may be cached and it will reduce load on your server.
招数21：
使用内容分发网络（CDN）托管图像和脚本。它可能会被缓存从而减少你服务器的负载。
(22)Use image sprites to retrieve smaller images in one download.
招数22：
使用图像精灵通过一次下载获取小的图像。
(23)Use AJAX to retrieve components asynchronously that may not be needed immediately, such as the content of a collapsed panel, content behind a tab, and so on.
招数23：
使用AJAX异步获取可能不需要立即加载的组件，比如伸缩面板的内容，TAB页后面的内容，等等。
(24)Make sure you’ve removed HTTP modules that aren’t being used (Windows authentication, for example), and that you’ve disabled services such as FTP and SMTP, if
you’re not using them.
招数24：
如果你不使用它，确保你已经移除了不使用的HTTP模块（比如，Windows认证），和禁用了FTP和SMTP服务。