graceful degradation

基本解释

First among them is its lack of provision for graceful degradation.
首先，它缺乏对功能退化的预防。
You will still have to provide fall-back support for IE6, however, either with conditional comments or through graceful degradation.
尽管如此你仍不得不通过条件注释或优雅降级的方法对IE6提供支持。
Browser support for some is limited, but CSS is designed for graceful degradation; a page should still be legible and usable if a style isn't applied.
浏览器对某些选择符的支持还不是很充分，但是 CSS 的设计允许平稳退化；如果无法应用某个样式，页面应该仍然是合法有效的。