Over the past few years, browsers have converged on using document.execCommand for clipboard interactions. It's great to have a single widely-supported way to integrate copy and paste into Web apps, but this came at a cost: clipboard access is synchronous, and can only read & write to the DOM.
客户端使用 GFWList 模式时观看流媒体。
HTTP Archieve有个统计，图片内容已经占到了互联网内容总量的 62% ，也就是说超过一半的流量和时间都用来下载图片。从性能优化的角度看，图片也绝对是优化的热点和重点之一，Google PageSpeed 或者 Yahoo 的 14 条性能优化规则无不把图片优化作为重要的优化手段，本文覆盖了 Web 图片优化的方方面面，从基本的图片格式选择、到尚未被广泛支持的响应式图片均有所提及。
Google Web Fundamentals 的说法我很喜欢：
图片优化既是一门艺术，也是一门科学，图片优化是一门艺术，是因为单个图片的压缩不存在最好的特定性方案，而图片优化之所以是一门科学，是因为许多开发得很出色的方法和算法可以明显减小图片的大小。要找到图片的最优设置，需要按照许多维度进行认真分析：格式能力、编码数据内容、像素尺寸等。
If it’s taking more than 3 seconds then you should be really worried about your site speed. Because No-one really likes slow loading websites.
There is no meaning of doing all the hard work to produce amazing content because if your website is too slow to load, the user is going to get bounced from your website.
So if you are really worried about your website speed and want to optimize it for your user and SEO you are at the right place.
Caching is a useful yet surprisingly complex feature of Web browsers.
In this article, we’ll explain the how the browser uses its cache to load pages faster, which factors determine cache duration, and how we can bypass the cache when necessary.
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