初学者概念：CSS选择器如何工作

你是CSS新手吗？这篇文章是给你的！也许理解CSS的最大关键是理解选择器。选择器允许您以特定的HTML元素为目标并对其应用样式。我们现在不要考虑样式，我们只需关注选择。在下面的示例中，CSS将位于一个名为样式.css从HTML文档中引用的索引.html. 它们是独立的文件，这是CSS最棒的地方，使设计远离文档，这就是HTML文件的样子： And the CSS file would contain just the selector blocks like you\"ll see below.ID selector #happy-cake {} Leveling Up ID selectors are the most powerful type of selector in terms of CSS specificity. Meaning that they beat out other types of selectors and the styles defined within win. That sounds good, but that\"s typically considered bad, because it\"s nice to have lower-specificity selectors that are easier to override when needed. Class Selector .module {} Leveling Up Class selectors are your friend. They are probably the most useful and versatile selectors out there. In part because they are well supported in all browsers. In part because you can add multiple classes (just separated by a space) on HTML elements. In part because there are JavaScript things you can do specifically for manipulating classes.Tag Selector h2 {} Hi, MomAnywhereLeveling Up Tag selectors are at their most useful when changing properties that are unique to that HTML element. Like setting the list-style在a上或tab-size在a上。另外，在重置样式表中，您特别尝试取消设置浏览器应用于某些元素的样式。通常，让一个类定义样式更有用，您可以在任何HTML元素上使用它。属性选择器 Leveling Up You might argue that attribute selectors are even more useful than classes because they have the same specificity value, but can be any attribute not just class，plus它们可以有一个您可以选择的值。不再是问题，但是IE 6不支持属性选择器。位置选择器 :nth-child(2) {} nopeyep, I\"m #2nope 除了第n个子级之外，还有几个不同的位置选择器。使用简单的表达式（如>其他伪选择器 :empty {} Leveling Up :empty是许多伪选择器中的一个，您可以通过其中的冒号（：）识别它们。它们通常表示仅凭元素和属性无法知道的内容。请注意，这些元素与伪元素略有不同，伪元素可以通过双冒号（：：）识别。他们负责按所选内容向页面中添加内容。可以将更多的升级选项组合在一起。例如： .module.news {/* Selects elements with BOTH of those classes */}#site-footer::after {/* Adds content after an element with that ID */}section[data-open] {/* Selects only section elements if they have this attribute */} 还有一些选择器组合，比如~和+和>会影响选择器，比如： .module > h2 {/* Select h2 elements that are direct children of an element with that class */} h2 + p {/* Select p elements that are directly following an h2 element */}li ~ li {/* Select li elements that are siblings (and following) another li element. */}/pre> 这里的CSS技巧有一个完整的历书，涵盖了CSS中的所有选择器以及属性

初学者概念：CSS选择器如何工作

admin_action_{$_REQUEST[‘action’]}

admin_footer-{$GLOBALS[‘hook_suffix’]}

customize_save_{$this->id_data[‘base’]}

customize_value_{$this->id_data[‘base’]}

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network_admin_edit_{$_GET[‘action’]}

network_sites_updated_message_{$_GET[‘updated’]}

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