MQ 未定义,- Html

简介

在网页开发中，我们经常需要使用到响应式设计，以便网页能够在不同设备上适配。Media Query（媒体查询）就是一种常用的响应式设计技术，它可以根据设备的不同特征（如屏幕尺寸、分辨率等）来应用不同的CSS样式规则。

在使用Media Query时，我们可以指定一系列CSS规则，然后将其应用到指定的媒体类型和特定的设备特征上。主流的设备特征包括屏幕宽度、高度、分辨率、方向等。

但有时候我们会看到一些只包含"- Html"的Media Query语句，这是什么意思呢？在这篇文章中，我们来探讨一下这个问题。

MQ未定义的含义

当我们看到一个Media Query语句中只包含"- Html"时，其实就是定义了一组默认的CSS规则，用于应用到所有HTML元素上。

例如：

@media (-webkit-min-device-pixel-ratio: 2), (min-resolution: 192dpi) and (min-width: 37.5em) and (-webkit-min-device-pixel-ratio: 1.5) and (-ms-high-contrast: active), only screen and (min-width: 37.5em), only screen and (min-device-width: 320px) and (max-device-width: 568px) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 375px) and (max-device-width: 812px) and (-webkit-min-device-pixel-ratio: 3), only screen and (min-device-width: 414px) and (max-device-width: 896px) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 414px) and (max-device-width: 736px) and (-webkit-min-device-pixel-ratio: 3), only screen and (min-device-width: 480px) and (max-device-width: 854px) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 568px) and (max-device-width: 812px) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 640px) and (max-device-width: 960px) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 640px) and (max-device-width: 1136px) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 667px) and (max-device-width: 1280px) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 667px) and (max-device-width: 1136px) and (-webkit-min-device-pixel-ratio: 3), only screen and (min-device-width: 720px) and (max-device-width: 1280px) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 736px) and (max-device-width: 1280px) and (-webkit-min-device-pixel-ratio: 3), only screen and (min-device-width: 768px) and (max-device-height: 1024px) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 768px) and (max-device-width: 1024px) and (orientation: landscape) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 768px) and (max-device-height: 1024px) and (orientation: portrait) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 768px) and (max-device-width: 1024px) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 768px) and (max-device-height: 1366px) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 834px) and (orientation: landscape) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 834px) and (orientation: portrait) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 834px) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 1024px) and (max-device-width: 1366px) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 1024px) and (max-device-height: 1366px) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 1024px) and (max-device-width: 1366px) and (orientation: landscape) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 1024px) and (max-device-height: 1366px) and (orientation: portrait) and (-webkit-min-device-pixel-ratio: 2), only screen and (min-device-width: 1024px) and (max-device-height: 1366px) and (-webkit-min-device-pixel-ratio: 2), all and (-ms-high-contrast: none), (min-width:310px) {

    /* 在所有HTML元素上应用的CSS规则 */
    color: #333;
    background-color: #f5f5f5;
}

我们可以看到，该语句中定义了一组CSS规则，应用于所有HTML元素。这也就意味着，无论页面中使用了什么元素，都将被应用这组CSS规则。

另外需要注意的是，"- Html"只是CSS语法的一部分，不是一个具体的特性或媒体类型。因此使用时需要注意语法的准确性。

总结

虽然在网页开发中并不经常使用"- Html"，但它是Media Query中的一个重要语法，值得我们了解一下。通过了解Media Query的相关知识，我们可以更好地掌握响应式设计技术，实现优秀的网页开发。