This rule is triggered when PageSpeed Insights detects that the system needs to make more network round trips to render the first screen content of a web page.

Overview

If the amount of data required exceeds the limit of the initial congestion window, the system needs to make more round trips between the server and the user's browser. If the user is using a network with a long delay time (for example, a mobile network), this problem will seriously delay the loading of web pages.

Recommendations

To speed up Web page loading, limit the size of data (HTML tags, pictures, CSS, and JavaScript) required to render the content of the first screen of a Web page. To do this, you can try the following methods:

• 結(jié)構(gòu)化HTML，以便首先加載關(guān)鍵的首屏內(nèi)容
• Reduce the amount of data used by resources

Structured HTML so that the key first screen content is loaded first

請(qǐng)首先加載網(wǎng)頁(yè)的主要內(nèi)容。結(jié)構(gòu)化網(wǎng)頁(yè)，以便服務(wù)器發(fā)出的初始響應(yīng)能發(fā)送必要數(shù)據(jù)，從而迅速呈現(xiàn)網(wǎng)頁(yè)的關(guān)鍵部分并暫緩呈現(xiàn)其余部分。這可能意味著，您必須將CSS拆分為兩個(gè)部分：負(fù)責(zé)調(diào)整內(nèi)容ATF部分的格式的內(nèi)嵌部分，以及可暫緩呈現(xiàn)的部分。

參考以下示例，了解有關(guān)如何結(jié)構(gòu)化網(wǎng)站以提高加載速度：

• 如果您的HTML先加載第三方小部件，再加載主要內(nèi)容，請(qǐng)將該加載順序更改為先加載主要內(nèi)容。
• If your site has a two-column layout (navigation sidebar plus article) and HTML loads the sidebar before the article, consider loading the article first.

Reduce the amount of data used by resources

如果經(jīng)過(guò)重新設(shè)計(jì)的網(wǎng)站可以在多個(gè)設(shè)備上正常運(yùn)行，并能首先加載關(guān)鍵內(nèi)容，請(qǐng)使用以下技術(shù)來(lái)減少呈現(xiàn)網(wǎng)頁(yè)所需的數(shù)據(jù)量：

• 縮減資源的大小：通過(guò)移除不必要的空格和評(píng)論來(lái)縮減HTML、CSS和JavaScript的大小。通過(guò)使用可重命名資源中變量名稱的工具，實(shí)現(xiàn)進(jìn)一步的優(yōu)化。
• 盡可能考慮Use CSS instead of pictures.
• 啟用壓縮功能

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