I develop an HTML widget that gets injected (as plain HTML, not iframe) to several websites.
The problem is that in some sites the style of my elements gets affected by the site's CSS (text alignment, underline, text spacing...).
Is there any way to prevent the site's CSS to affect the style of injected elements?
如果你想重置所有 CSS 属性，你可以这样做。这是一个大文件，可能不是最好的解决方案，但它确实有效。
.yourContainer * {
-webkit-align-content: stretch; -moz-align-content: stretch; align-content: stretch;
-webkit-align-items: stretch; -moz-align-items: stretch; align-items: stretch;
-webkit-align-self: stretch; -moz-align-self: stretch; align-self: stretch;
-webkit-animation-delay: 0s; -moz-animation-delay: 0s; animation-delay: 0s;
-webkit-animation-direction: normal; -moz-animation-direction: normal; animation-direction: normal;
-webkit-animation-duration: 0s; -moz-animation-duration: 0s; animation-duration: 0s;
-webkit-animation-fill-mode: none; -moz-animation-fill-mode: none; animation-fill-mode: none;
-webkit-animation-iteration-count: 1; -moz-animation-iteration-count: 1; animation-iteration-count: 1;
-webkit-animation-name: none; -moz-animation-name: none; animation-name: none;
-webkit-animation-play-state: running; -moz-animation-play-state: running; animation-play-state: running;
-webkit-animation-timing-function: ease; -moz-animation-timing-function: ease; animation-timing-function: ease;
-webkit-app-region: no-drag; -moz-app-region: no-drag; app-region: no-drag;
-webkit-appearance: none; -moz-appearance: none; appearance: none;
-webkit-backface-visibility: visible; -moz-backface-visibility: visible; backface-visibility: visible;
-webkit-background-clip: border-box; -moz-background-clip: border-box; background-clip: border-box;
-webkit-background-composite: source-over; -moz-background-composite: source-over; background-composite: source-over;
-webkit-background-origin: padding-box; -moz-background-origin: padding-box; background-origin: padding-box;
-webkit-background-size: auto; -moz-background-size: auto; background-size: auto;
-webkit-border-fit: border; -moz-border-fit: border; border-fit: border;
-webkit-border-horizontal-spacing: 0px; -moz-border-horizontal-spacing: 0px; border-horizontal-spacing: 0px;
-webkit-border-image: none; -moz-border-image: none; border-image: none;
-webkit-border-vertical-spacing: 0px; -moz-border-vertical-spacing: 0px; border-vertical-spacing: 0px;
-webkit-box-align: stretch; -moz-box-align: stretch; box-align: stretch;
-webkit-box-decoration-break: slice; -moz-box-decoration-break: slice; box-decoration-break: slice;
-webkit-box-direction: normal; -moz-box-direction: normal; box-direction: normal;
-webkit-box-flex: 0; -moz-box-flex: 0; box-flex: 0;
-webkit-box-flex-group: 1; -moz-box-flex-group: 1; box-flex-group: 1;
-webkit-box-lines: single; -moz-box-lines: single; box-lines: single;
-webkit-box-ordinal-group: 1; -moz-box-ordinal-group: 1; box-ordinal-group: 1;
-webkit-box-orient: horizontal; -moz-box-orient: horizontal; box-orient: horizontal;
-webkit-box-pack: start; -moz-box-pack: start; box-pack: start;
-webkit-box-reflect: none; -moz-box-reflect: none; box-reflect: none;
-webkit-box-shadow: none; -moz-box-shadow: none; box-shadow: none;
-webkit-clip-path: none; -moz-clip-path: none; clip-path: none;
-webkit-color-correction: default; -moz-color-correction: default; color-correction: default;
-webkit-column-axis: auto; -moz-column-axis: auto; column-axis: auto;
-webkit-column-break-after: auto; -moz-column-break-after: auto; column-break-after: auto;
-webkit-column-break-before: auto; -moz-column-break-before: auto; column-break-before: auto;
-webkit-column-break-inside: auto; -moz-column-break-inside: auto; column-break-inside: auto;
-webkit-column-count: auto; -moz-column-count: auto; column-count: auto;
-webkit-column-gap: normal; -moz-column-gap: normal; column-gap: normal;
-webkit-column-progression: normal; -moz-column-progression: normal; column-progression: normal;
-webkit-column-rule-color: rgb(0, 0, 0); -moz-column-rule-color: rgb(0, 0, 0); column-rule-color: rgb(0, 0, 0);
-webkit-column-rule-style: none; -moz-column-rule-style: none; column-rule-style: none;
-webkit-column-rule-width: 0px; -moz-column-rule-width: 0px; column-rule-width: 0px;
-webkit-column-span: none; -moz-column-span: none; column-span: none;
-webkit-column-width: auto; -moz-column-width: auto; column-width: auto;
-webkit-filter: none; -moz-filter: none; filter: none;
-webkit-flex-basis: auto; -moz-flex-basis: auto; flex-basis: auto;
-webkit-flex-direction: row; -moz-flex-direction: row; flex-direction: row;
-webkit-flex-grow: 0; -moz-flex-grow: 0; flex-grow: 0;
-webkit-flex-shrink: 1; -moz-flex-shrink: 1; flex-shrink: 1;
-webkit-flex-wrap: nowrap; -moz-flex-wrap: nowrap; flex-wrap: nowrap;
-webkit-flow-from: none; -moz-flow-from: none; flow-from: none;
-webkit-flow-into: none; -moz-flow-into: none; flow-into: none;
-webkit-font-kerning: auto; -moz-font-kerning: auto; font-kerning: auto;
-webkit-font-smoothing: auto; -moz-font-smoothing: auto; font-smoothing: auto;
-webkit-font-variant-ligatures: normal; -moz-font-variant-ligatures: normal; font-variant-ligatures: normal;
-webkit-grid-after: auto; -moz-grid-after: auto; grid-after: auto;
-webkit-grid-auto-columns: auto; -moz-grid-auto-columns: auto; grid-auto-columns: auto;
-webkit-grid-auto-flow: none; -moz-grid-auto-flow: none; grid-auto-flow: none;
-webkit-grid-auto-rows: auto; -moz-grid-auto-rows: auto; grid-auto-rows: auto;
-webkit-grid-before: auto; -moz-grid-before: auto; grid-before: auto;
-webkit-grid-columns: none; -moz-grid-columns: none; grid-columns: none;
-webkit-grid-end: auto; -moz-grid-end: auto; grid-end: auto;
-webkit-grid-rows: none; -moz-grid-rows: none; grid-rows: none;
-webkit-grid-start: auto; -moz-grid-start: auto; grid-start: auto;
-webkit-highlight: none; -moz-highlight: none; highlight: none;
-webkit-hyphenate-character: auto; -moz-hyphenate-character: auto; hyphenate-character: auto;
-webkit-hyphenate-limit-after: auto; -moz-hyphenate-limit-after: auto; hyphenate-limit-after: auto;
-webkit-hyphenate-limit-before: auto; -moz-hyphenate-limit-before: auto; hyphenate-limit-before: auto;
-webkit-hyphenate-limit-lines: no-limit; -moz-hyphenate-limit-lines: no-limit; hyphenate-limit-lines: no-limit;
-webkit-hyphens: manual; -moz-hyphens: manual; hyphens: manual;
-webkit-justify-content: flex-start; -moz-justify-content: flex-start; justify-content: flex-start;
-webkit-line-align: none; -moz-line-align: none; line-align: none;
-webkit-line-box-contain: block inline replaced; -moz-line-box-contain: block inline replaced; line-box-contain: block inline replaced;
-webkit-line-break: auto; -moz-line-break: auto; line-break: auto;
-webkit-line-clamp: none; -moz-line-clamp: none; line-clamp: none;
-webkit-line-grid: none; -moz-line-grid: none; line-grid: none;
-webkit-line-snap: none; -moz-line-snap: none; line-snap: none;
-webkit-locale: auto; -moz-locale: auto; locale: auto;
-webkit-margin-after-collapse: collapse; -moz-margin-after-collapse: collapse; margin-after-collapse: collapse;
-webkit-margin-before-collapse: collapse; -moz-margin-before-collapse: collapse; margin-before-collapse: collapse;
-webkit-marquee-direction: auto; -moz-marquee-direction: auto; marquee-direction: auto;
-webkit-marquee-increment: 6px; -moz-marquee-increment: 6px; marquee-increment: 6px;
-webkit-marquee-repetition: infinite; -moz-marquee-repetition: infinite; marquee-repetition: infinite;
-webkit-marquee-style: scroll; -moz-marquee-style: scroll; marquee-style: scroll;
-webkit-mask-box-image: none; -moz-mask-box-image: none; mask-box-image: none;
-webkit-mask-box-image-outset: 0px; -moz-mask-box-image-outset: 0px; mask-box-image-outset: 0px;
-webkit-mask-box-image-repeat: stretch; -moz-mask-box-image-repeat: stretch; mask-box-image-repeat: stretch;
-webkit-mask-box-image-slice: 0 fill; -moz-mask-box-image-slice: 0 fill; mask-box-image-slice: 0 fill;
-webkit-mask-box-image-source: none; -moz-mask-box-image-source: none; mask-box-image-source: none;
-webkit-mask-box-image-width: auto; -moz-mask-box-image-width: auto; mask-box-image-width: auto;
-webkit-mask-clip: border-box; -moz-mask-clip: border-box; mask-clip: border-box;
-webkit-mask-composite: source-over; -moz-mask-composite: source-over; mask-composite: source-over;
-webkit-mask-image: none; -moz-mask-image: none; mask-image: none;
-webkit-mask-origin: border-box; -moz-mask-origin: border-box; mask-origin: border-box;
-webkit-mask-position: 0% 0%; -moz-mask-position: 0% 0%; mask-position: 0% 0%;
-webkit-mask-repeat: repeat; -moz-mask-repeat: repeat; mask-repeat: repeat;
-webkit-mask-size: auto; -moz-mask-size: auto; mask-size: auto;
-webkit-nbsp-mode: normal; -moz-nbsp-mode: normal; nbsp-mode: normal;
-webkit-order: 0; -moz-order: 0; order: 0;
-webkit-perspective: none; -moz-perspective: none; perspective: none;
-webkit-perspective-origin: 640px 345px; -moz-perspective-origin: 640px 345px; perspective-origin: 640px 345px;
-webkit-print-color-adjust: economy; -moz-print-color-adjust: economy; print-color-adjust: economy;
-webkit-region-break-after: auto; -moz-region-break-after: auto; region-break-after: auto;
-webkit-region-break-before: auto; -moz-region-break-before: auto; region-break-before: auto;
-webkit-region-break-inside: auto; -moz-region-break-inside: auto; region-break-inside: auto;
-webkit-region-overflow: auto; -moz-region-overflow: auto; region-overflow: auto;
-webkit-rtl-ordering: logical; -moz-rtl-ordering: logical; rtl-ordering: logical;
-webkit-shape-inside: outside-shape; -moz-shape-inside: outside-shape; shape-inside: outside-shape;
-webkit-shape-margin: 0px; -moz-shape-margin: 0px; shape-margin: 0px;
-webkit-shape-outside: auto; -moz-shape-outside: auto; shape-outside: auto;
-webkit-shape-padding: 0px; -moz-shape-padding: 0px; shape-padding: 0px;
-webkit-svg-shadow: none; -moz-svg-shadow: none; svg-shadow: none;
-webkit-tap-highlight-color: rgba(0, 0, 0, 0.180392); -moz-tap-highlight-color: rgba(0, 0, 0, 0.180392); tap-highlight-color: rgba(0, 0, 0, 0.180392);
-webkit-text-combine: none; -moz-text-combine: none; text-combine: none;
-webkit-text-decorations-in-effect: none; -moz-text-decorations-in-effect: none; text-decorations-in-effect: none;
-webkit-text-emphasis-color: rgb(0, 0, 0); -moz-text-emphasis-color: rgb(0, 0, 0); text-emphasis-color: rgb(0, 0, 0);
-webkit-text-emphasis-position: over; -moz-text-emphasis-position: over; text-emphasis-position: over;
-webkit-text-emphasis-style: none; -moz-text-emphasis-style: none; text-emphasis-style: none;
-webkit-text-fill-color: rgb(0, 0, 0); -moz-text-fill-color: rgb(0, 0, 0); text-fill-color: rgb(0, 0, 0);
-webkit-text-orientation: vertical-right; -moz-text-orientation: vertical-right; text-orientation: vertical-right;
-webkit-text-security: none; -moz-text-security: none; text-security: none;
-webkit-text-stroke-color: rgb(0, 0, 0); -moz-text-stroke-color: rgb(0, 0, 0); text-stroke-color: rgb(0, 0, 0);
-webkit-text-stroke-width: 0px; -moz-text-stroke-width: 0px; text-stroke-width: 0px;
-webkit-transform: none; -moz-transform: none; transform: none;
-webkit-transform-origin: 640px 345px; -moz-transform-origin: 640px 345px; transform-origin: 640px 345px;
-webkit-transform-style: flat; -moz-transform-style: flat; transform-style: flat;
-webkit-transition-delay: 0s; -moz-transition-delay: 0s; transition-delay: 0s;
-webkit-transition-duration: 0s; -moz-transition-duration: 0s; transition-duration: 0s;
-webkit-transition-property: all; -moz-transition-property: all; transition-property: all;
-webkit-transition-timing-function: ease; -moz-transition-timing-function: ease; transition-timing-function: ease;
-webkit-user-drag: auto; -moz-user-drag: auto; user-drag: auto;
-webkit-user-modify: read-only; -moz-user-modify: read-only; user-modify: read-only;
-webkit-user-select: text; -moz-user-select: text; user-select: text;
-webkit-wrap-flow: auto; -moz-wrap-flow: auto; wrap-flow: auto;
-webkit-wrap-through: wrap; -moz-wrap-through: wrap; wrap-through: wrap;
-webkit-writing-mode: horizontal-tb; -moz-writing-mode: horizontal-tb; writing-mode: horizontal-tb;
alignment-baseline: auto;
background-attachment: scroll;
background-clip: border-box;
background-color: rgba(0, 0, 0, 0);
background-image: none;
background-origin: padding-box;
background-position: 0% 0%;
background-repeat: repeat;
background-size: auto;
baseline-shift: baseline;
border-bottom-color: rgb(0, 0, 0);
border-bottom-left-radius: 0px;
border-bottom-right-radius: 0px;
border-bottom-style: none;
border-bottom-width: 0px;
border-collapse: separate;
border-image-outset: 0px;
border-image-repeat: stretch;
border-image-slice: 100%;
border-image-source: none;
border-image-width: 1;
border-left-color: rgb(0, 0, 0);
border-left-style: none;
border-left-width: 0px;
border-right-color: rgb(0, 0, 0);
border-right-style: none;
border-right-width: 0px;
border-top-color: rgb(0, 0, 0);
border-top-left-radius: 0px;
border-top-right-radius: 0px;
border-top-style: none;
border-top-width: 0px;
bottom: auto;
box-shadow: none;
box-sizing: content-box;
caption-side: top;
clear: none;
clip: auto;
clip-path: none;
clip-rule: nonzero;
color: rgb(0, 0, 0);
color-interpolation: srgb;
color-interpolation-filters: linearrgb;
color-rendering: auto;
cursor: auto;
direction: ltr;
display: block;
dominant-baseline: auto;
empty-cells: show;
fill: #000000;
fill-opacity: 1;
fill-rule: nonzero;
filter: none;
float: none;
flood-color: rgb(0, 0, 0);
flood-opacity: 1;
font-family: sans-serif;
font-size: 16px;
font-style: normal;
font-variant: normal;
font-weight: normal;
glyph-orientation-horizontal: 0deg;
glyph-orientation-vertical: auto;
height: auto;
image-rendering: auto;
kerning: 0;
left: auto;
letter-spacing: normal;
lighting-color: rgb(255, 255, 255);
line-height: normal;
list-style-image: none;
list-style-position: outside;
list-style-type: disc;
margin-bottom: 0px;
margin-left: 0px;
margin-right: 0px;
margin-top: 0px;
marker-end: none;
marker-mid: none;
marker-start: none;
mask: none;
mask-type: luminance;
max-height: none;
max-width: none;
min-height: 0px;
min-width: 0px;
opacity: 1;
orphans: auto;
outline-color: rgb(0, 0, 0);
outline-offset: 0px;
outline-style: none;
outline-width: 0px;
overflow-wrap: normal;
overflow-x: visible;
overflow-y: visible;
padding-bottom: 0px;
padding-left: 0px;
padding-right: 0px;
padding-top: 0px;
page-break-after: auto;
page-break-before: auto;
page-break-inside: auto;
pointer-events: auto;
position: static;
resize: none;
right: auto;
shape-rendering: auto;
speak: normal;
stop-color: rgb(0, 0, 0);
stop-opacity: 1;
stroke: none;
stroke-dasharray: none;
stroke-dashoffset: 0;
stroke-linecap: butt;
stroke-linejoin: miter;
stroke-miterlimit: 4;
stroke-opacity: 1;
stroke-width: 1;
tab-size: 8;
table-layout: auto;
text-align: start;
text-anchor: start;
text-decoration: none;
text-indent: 0px;
text-overflow: clip;
text-rendering: auto;
text-shadow: none;
text-transform: none;
top: auto;
transition-delay: 0s;
transition-duration: 0s;
transition-property: all;
transition-timing-function: ease;
unicode-bidi: normal;
vector-effect: none;
vertical-align: baseline;
visibility: visible;
white-space: normal;
widows: auto;
width: auto;
word-break: normal;
word-spacing: 0px;
word-wrap: normal;
writing-mode: lr-tb;
z-index: auto;
zoom: 1;
}
通常没有，没有。归根结底，如果您将 HTML 代码放入其他人的站点，您就是在隐含地让他们控制该 HTML 的样式。
即使 using!important也可以用另一种!important样式覆盖，或者在最坏的情况下通过一点 Javascript 直接在元素上设置样式。（无论如何，!important这被认为是不好的做法，所以你可能不想这样做，对吧）
当然，您可以自己使用 Javascript 来设置样式，但是在您完成之后，网站所有者仍然容易受到同样的影响。
唯一真正可行的解决方案是将整个小部件放入 iframe。这就是谷歌为他们的广告等所做的事情。这将很好地将您的小部件代码与主站点隔离开来，并防止站点所有者无意中覆盖您的样式的任何可能性。他们可能仍然有办法解决这个问题，但是当您处理跨站点 iframe 时，它会变得更加困难，因为内置的浏览器安全限制开始发挥作用。
但真正的问题是：你真的需要这样做吗？保持您定义的样式对您的样式有多重要？如果您的小部件使用该站点的默认字体呈现，也许您的小部件在特定站点上看起来更好？也许网站所有者对特定字体或颜色有公司要求？（有些公司可能对此非常挑剔）。当然，如果它在他们的网站上，他们至少应该有一定程度的控制权？如果他们完成后看起来很垃圾，那是他们的错。
现在我知道上面的段落并不适用于所有人。也许你问这个是因为你不希望用户隐藏你的版权文本，或者类似的东西。但是在某些情况下，您确实需要问自己一个问题，即您是否为此而施加限制；他们是否真的值得付出努力，或者他们是否可能只会惹恼想要做一些完全合法的事情的用户。
看看这里： http: //meyerweb.com/eric/tools/css/reset/。将代码粘贴到小部件样式表的顶部，它将重置几乎所有可能影响显示的 CSS 属性。如果你不想访问链接，这里是：
html, body, div, span, applet, object, iframe,
h1, h2, h3, h4, h5, h6, p, blockquote, pre,
a, abbr, acronym, address, big, cite, code,
del, dfn, em, img, ins, kbd, q, s, samp,
small, strike, strong, sub, sup, tt, var,
b, u, i, center,
dl, dt, dd, ol, ul, li,
fieldset, form, label, legend,
table, caption, tbody, tfoot, thead, tr, th, td,
article, aside, canvas, details, embed,
figure, figcaption, footer, header, hgroup,
menu, nav, output, ruby, section, summary,
time, mark, audio, video {
margin: 0;
padding: 0;
border: 0;
font-size: 100%;
font: inherit;
vertical-align: baseline;
background: none;
}
/* HTML5 display-role reset for older browsers */
article, aside, details, figcaption, figure,
footer, header, hgroup, menu, nav, section {
display: block;
}
body {
line-height: 1;
}
ol, ul {
list-style: none;
}
blockquote, q {
quotes: none;
}
blockquote:before, blockquote:after,
q:before, q:after {
content: '';
content: none;
}
table {
border-collapse: collapse;
border-spacing: 0;
}
CSS的本质是继承。即，如果您不向元素发送属性，它将从其父元素中获取。据我了解，您正在将小部件添加为代码。我的意思是您的代码被注入到另一个页面中，并且不涉及 iframe。因此，您的样式应该是内联样式，例如：
<div class="widget" style="padding: 0;">
...
</div>
您可能尝试的第一个解决方案是将重置样式放在您的最顶层容器中。所以它的所有孩子都从那里继承了缺失的属性。然而这并不是那么好，因为有大量的属性并且直接将它们添加到标签中看起来很奇怪。
使用 !important 就足够了，但这仅在您知道哪种样式将被更改的情况下。
我认为，如果您不使用 iframe，则很难拥有绝对自定义外观的小部件。你可以尝试一些疯狂的事情，比如
为封装注入的 div 创建一个 id，然后根据需要设置样式。这将始终保持完好无损。否则，你无法阻止事情的发生，只有保护。
在你的 css 中尽可能具体。因此，假设您有以下 HTML
<div id="myWidget">
<div class="someContent">test</div>
</div>
并且您想告诉 someContent 需要是红色的，请使用以下 css：
#myWidget div.someContent{#ff0000;}