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CSS 参考手册

CSS 参考手册 CSS 选择器 CSS 语音参考 CSS Web安全字体 CSS 单位 CSS 颜色 CSS 合法颜色值 CSS 颜色名称 CSS 颜色十六进制值 CSS 浏览器支持

CSS 属性

align-contentalign-itemsalign-selfanimationanimation-delayanimation-directionanimation-durationanimation-fill-modeanimation-iteration-countanimation-nameanimation-play-stateanimation-timing-function appearance backface-visibility background background-attachment background-clip background-color background-image background-origin background-position background-repeat background-size border border-bottom border-bottom-color border-bottom-left-radiusborder-bottom-right-radius border-bottom-style border-bottom-width border-collapse border-color border-imageborder-image-outsetborder-image-repeatborder-image-sliceborder-image-sourceborder-image-width border-left border-left-color border-left-style border-left-width border-radius border-right border-right-color border-right-style border-right-width border-spacing border-style border-top border-top-color border-top-left-radiusborder-top-right-radius border-top-style border-top-width border-width bottom box-align box-direction box-flex box-flex-group box-lines box-ordinal-group box-orient box-pack box-shadow box-sizing caption-side clear clip color column-count column-fill column-gap column-rule column-rule-color column-rule-style column-rule-width column-span column-width columns content counter-increment counter-reset cursor direction display empty-cells flexflex-basisflex-directionflex-flowflex-growflex-shrinkflex-wrap float font @font-face font-family font-size font-size-adjustfont-stretch font-style font-variant font-weight grid-columns grid-rows hanging-punctuation height icon justify-content@keyframes left letter-spacing line-height list-style list-style-image list-style-position list-style-type margin margin-bottom margin-left margin-right margin-top max-height max-width min-height min-width nav-down nav-index nav-left nav-right nav-up opacity order outline outline-color outline-offset outline-style outline-width overflow overflow-x overflow-y padding padding-bottom padding-left padding-right padding-top page-break-after page-break-before page-break-inside perspective perspective-origin position punctuation-trim quotes resize right rotation tab-size table-layout target target-name target-new target-position text-align text-align-last text-decoration text-decoration-colortext-decoration-linetext-decoration-style text-indent text-justify text-outline text-overflow text-shadow text-transform text-wrap top transform transform-origin transform-style transition transition-delaytransition-duration transition-property transition-timing-function unicode-bidi vertical-align visibility white-space width word-break word-spacing word-wrap z-index

 

CSS :optional选择器

完整CSS选择器参考手册 完整CSS选择器参考手册

实例

如果 input 元素没有设置 "required" 属性,设置其为黄色:

input:optional
{
background-color: yellow;
}

尝试一下 »

定义和使用

:optional 选择器在表单元素是可选项时设置指定样式。

表单元素中如果没有特别设置 required 属性即为 optional 属性。

注意: :optional 选择器只适用于表单元素: input, select 和 textarea。


浏览器支持

Internet ExplorerFirefoxOperaGoogle ChromeSafari

:optional 选择器支持所有主流浏览器。

Internet Explorer 9 及更早IE版本不止 :required 选择器。


CSS 语法

:optional
{
css 声明;
}


相关页面

CSS 选择器 :required


完整CSS选择器参考手册 完整CSS选择器参考手册