Why is there a time span between different network requests?

问题

I'm optimizing the loading times in a web app and I don't know what's the problem. Firebug's Net panel is showing time holes between requests.

Can someone explain me this chart?

回答1:

The gap between the requests can have two reasons:

1. Time needed to parse the requested page

   When you request a URL, the browser needs to parse the returned contents to check whether they contain URLs to other ressources like JavaScripts, CSS files, images, etc. Subsequently requested ressources need to be parsed, too. So e.g. CSS files can contain references to images. Though the contents of the CSS file first need to be parsed to get those URLs.

2. Dynamically requested ressources

   Using JavaScript resources can be requested asynchronously. These requests can be triggered e.g. through AJAX or by dynamically inserting DOM nodes like <img src="xyz.png" alt=""> into the page.

来源：https://stackoverflow.com/questions/31345263/why-is-there-a-time-span-between-different-network-requests