You're using the shorthand for the outline-* properties; auto represents the value for outline-style and auto itself means that it's up to the browser to decide what to do based on the context of the element.
我想指出的是，在 IE 中 auto 不会显示任何内容，您必须明确声明要使用的边框类型。 Alex K 的链接很好地演示了其他流行浏览器的工作原理。
I would just like to point out that in IE auto doesn't show anything, and you'll have to explicitly declare what type of border you want to use. Alex K's link is a good demonstration of how other popular browsers work.
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您正在使用
outline-*属性；auto表示outline-style的值，而auto本身意味着由浏览器根据内容的上下文来决定做什么元素。You're using the shorthand for the
outline-*properties;autorepresents the value foroutline-styleandautoitself means that it's up to the browser to decide what to do based on the context of the element.我想指出的是，在 IE 中
auto不会显示任何内容，您必须明确声明要使用的边框类型。 Alex K 的链接很好地演示了其他流行浏览器的工作原理。I would just like to point out that in IE
autodoesn't show anything, and you'll have to explicitly declare what type of border you want to use. Alex K's link is a good demonstration of how other popular browsers work.