Reset/remove CSS styles for element only

I'm sure this must have been mentioned/asked before but have been searching for an age with no luck, my terminology must be wrong!

I vaguely remember a tweet I saw a while ago that suggested that there was a css rule available that would remove any styles previously set in the stylesheet for a particular element.

A good use example might be in a mobile-first RWD site where much of the styling used for a particular element in the small-screen views needs 'resetting' or removing for the same element in the desktop view.

A css rule that could achieve something like:

.element {
  all: none;
}

Example usage:

/* mobile first */
.element {
   margin: 0 10;
   transform: translate3d(0, 0, 0);
   z-index: 50;
   display: block;
   etc..
   etc..
}

@media only screen and (min-width: 980px) {
  .element {
    all: none;
  }
}

So we could quickly remove or re-set styling without having to declare every property.

Makes sense?

The CSS3 keyword initial sets the CSS3 property to the initial value as defined in the spec. The initial keyword has broad browser support except for the IE and Opera Mini families.

Since IE's lack of support may cause issue here are some of the ways you can reset some CSS properties to their initial values:

.reset-this {
    animation : none;
    animation-delay : 0;
    animation-direction : normal;
    animation-duration : 0;
    animation-fill-mode : none;
    animation-iteration-count : 1;
    animation-name : none;
    animation-play-state : running;
    animation-timing-function : ease;
    backface-visibility : visible;
    background : 0;
    background-attachment : scroll;
    background-clip : border-box;
    background-color : transparent;
    background-image : none;
    background-origin : padding-box;
    background-position : 0 0;
    background-position-x : 0;
    background-position-y : 0;
    background-repeat : repeat;
    background-size : auto auto;
    border : 0;
    border-style : none;
    border-width : medium;
    border-color : inherit;
    border-bottom : 0;
    border-bottom-color : inherit;
    border-bottom-left-radius : 0;
    border-bottom-right-radius : 0;
    border-bottom-style : none;
    border-bottom-width : medium;
    border-collapse : separate;
    border-image : none;
    border-left : 0;
    border-left-color : inherit;
    border-left-style : none;
    border-left-width : medium;
    border-radius : 0;
    border-right : 0;
    border-right-color : inherit;
    border-right-style : none;
    border-right-width : medium;
    border-spacing : 0;
    border-top : 0;
    border-top-color : inherit;
    border-top-left-radius : 0;
    border-top-right-radius : 0;
    border-top-style : none;
    border-top-width : medium;
    bottom : auto;
    box-shadow : none;
    box-sizing : content-box;
    caption-side : top;
    clear : none;
    clip : auto;
    color : inherit;
    columns : auto;
    column-count : auto;
    column-fill : balance;
    column-gap : normal;
    column-rule : medium none currentColor;
    column-rule-color : currentColor;
    column-rule-style : none;
    column-rule-width : none;
    column-span : 1;
    column-width : auto;
    content : normal;
    counter-increment : none;
    counter-reset : none;
    cursor : auto;
    direction : ltr;
    display : inline;
    empty-cells : show;
    float : none;
    font : normal;
    font-family : inherit;
    font-size : medium;
    font-style : normal;
    font-variant : normal;
    font-weight : normal;
    height : auto;
    hyphens : none;
    left : auto;
    letter-spacing : normal;
    line-height : normal;
    list-style : none;
    list-style-image : none;
    list-style-position : outside;
    list-style-type : disc;
    margin : 0;
    margin-bottom : 0;
    margin-left : 0;
    margin-right : 0;
    margin-top : 0;
    max-height : none;
    max-width : none;
    min-height : 0;
    min-width : 0;
    opacity : 1;
    orphans : 0;
    outline : 0;
    outline-color : invert;
    outline-style : none;
    outline-width : medium;
    overflow : visible;
    overflow-x : visible;
    overflow-y : visible;
    padding : 0;
    padding-bottom : 0;
    padding-left : 0;
    padding-right : 0;
    padding-top : 0;
    page-break-after : auto;
    page-break-before : auto;
    page-break-inside : auto;
    perspective : none;
    perspective-origin : 50% 50%;
    position : static;
    /* May need to alter quotes for different locales (e.g fr) */
    quotes : '\201C' '\201D' '\2018' '\2019';
    right : auto;
    tab-size : 8;
    table-layout : auto;
    text-align : inherit;
    text-align-last : auto;
    text-decoration : none;
    text-decoration-color : inherit;
    text-decoration-line : none;
    text-decoration-style : solid;
    text-indent : 0;
    text-shadow : none;
    text-transform : none;
    top : auto;
    transform : none;
    transform-style : flat;
    transition : none;
    transition-delay : 0s;
    transition-duration : 0s;
    transition-property : none;
    transition-timing-function : ease;
    unicode-bidi : normal;
    vertical-align : baseline;
    visibility : visible;
    white-space : normal;
    widows : 0;
    width : auto;
    word-spacing : normal;
    z-index : auto;
    /* basic modern patch */
    all: initial;
    all: unset;
}

/* basic modern patch */

#reset-this-root {
    all: initial;
    * {
        all: unset;
    }
}

• Relevent github repo with a december 2017 more exaustive list
• Related
• Related from MDN
• Related W3C specs

As mentioned in a comment by @user566245 :

> this is correct in principle, but individual mileage may vary. For > example certain elements like textarea by default have a border, > applying this reset will render those textarea's border less.

---

JAVASCRIPT ?

Nobody thought about other than css to reset css? Yes?

There is that snip fully relevant : https://stackoverflow.com/a/14791113/845310

> getElementsByTagName("*") will return all elements from DOM. Then you > may set styles for each element in the collection:

answered Feb 9 '13 at 20:15 by VisioN

var allElements = document.getElementsByTagName("*");
for (var i = 0, len = allElements.length; i < len; i++) {
    var element = allElements[i];
    // element.style.border = ...
}

---

With all this said; i don't think a css reset is something feasable unless we end up with only one web browser .. if the 'default' is set by browser in the end.

For comparison, here is Firefox 40.0 values list for a <blockquote style="all: unset;font-style: oblique"> where font-style: oblique triggers DOM operation.

align-content: unset;
align-items: unset;
align-self: unset;
animation: unset;
appearance: unset;
backface-visibility: unset;
background-blend-mode: unset;
background: unset;
binding: unset;
block-size: unset;
border-block-end: unset;
border-block-start: unset;
border-collapse: unset;
border-inline-end: unset;
border-inline-start: unset;
border-radius: unset;
border-spacing: unset;
border: unset;
bottom: unset;
box-align: unset;
box-decoration-break: unset;
box-direction: unset;
box-flex: unset;
box-ordinal-group: unset;
box-orient: unset;
box-pack: unset;
box-shadow: unset;
box-sizing: unset;
caption-side: unset;
clear: unset;
clip-path: unset;
clip-rule: unset;
clip: unset;
color-adjust: unset;
color-interpolation-filters: unset;
color-interpolation: unset;
color: unset;
column-fill: unset;
column-gap: unset;
column-rule: unset;
columns: unset;
content: unset;
control-character-visibility: unset;
counter-increment: unset;
counter-reset: unset;
cursor: unset;
display: unset;
dominant-baseline: unset;
empty-cells: unset;
fill-opacity: unset;
fill-rule: unset;
fill: unset;
filter: unset;
flex-flow: unset;
flex: unset;
float-edge: unset;
float: unset;
flood-color: unset;
flood-opacity: unset;
font-family: unset;
font-feature-settings: unset;
font-kerning: unset;
font-language-override: unset;
font-size-adjust: unset;
font-size: unset;
font-stretch: unset;
font-style: oblique;
font-synthesis: unset;
font-variant: unset;
font-weight: unset;
font: ;
force-broken-image-icon: unset;
height: unset;
hyphens: unset;
image-orientation: unset;
image-region: unset;
image-rendering: unset;
ime-mode: unset;
inline-size: unset;
isolation: unset;
justify-content: unset;
justify-items: unset;
justify-self: unset;
left: unset;
letter-spacing: unset;
lighting-color: unset;
line-height: unset;
list-style: unset;
margin-block-end: unset;
margin-block-start: unset;
margin-inline-end: unset;
margin-inline-start: unset;
margin: unset;
marker-offset: unset;
marker: unset;
mask-type: unset;
mask: unset;
max-block-size: unset;
max-height: unset;
max-inline-size: unset;
max-width: unset;
min-block-size: unset;
min-height: unset;
min-inline-size: unset;
min-width: unset;
mix-blend-mode: unset;
object-fit: unset;
object-position: unset;
offset-block-end: unset;
offset-block-start: unset;
offset-inline-end: unset;
offset-inline-start: unset;
opacity: unset;
order: unset;
orient: unset;
outline-offset: unset;
outline-radius: unset;
outline: unset;
overflow: unset;
padding-block-end: unset;
padding-block-start: unset;
padding-inline-end: unset;
padding-inline-start: unset;
padding: unset;
page-break-after: unset;
page-break-before: unset;
page-break-inside: unset;
paint-order: unset;
perspective-origin: unset;
perspective: unset;
pointer-events: unset;
position: unset;
quotes: unset;
resize: unset;
right: unset;
ruby-align: unset;
ruby-position: unset;
scroll-behavior: unset;
scroll-snap-coordinate: unset;
scroll-snap-destination: unset;
scroll-snap-points-x: unset;
scroll-snap-points-y: unset;
scroll-snap-type: unset;
shape-rendering: unset;
stack-sizing: unset;
stop-color: unset;
stop-opacity: unset;
stroke-dasharray: unset;
stroke-dashoffset: unset;
stroke-linecap: unset;
stroke-linejoin: unset;
stroke-miterlimit: unset;
stroke-opacity: unset;
stroke-width: unset;
stroke: unset;
tab-size: unset;
table-layout: unset;
text-align-last: unset;
text-align: unset;
text-anchor: unset;
text-combine-upright: unset;
text-decoration: unset;
text-emphasis-position: unset;
text-emphasis: unset;
text-indent: unset;
text-orientation: unset;
text-overflow: unset;
text-rendering: unset;
text-shadow: unset;
text-size-adjust: unset;
text-transform: unset;
top: unset;
transform-origin: unset;
transform-style: unset;
transform: unset;
transition: unset;
user-focus: unset;
user-input: unset;
user-modify: unset;
user-select: unset;
vector-effect: unset;
vertical-align: unset;
visibility: unset;
white-space: unset;
width: unset;
will-change: unset;
window-dragging: unset;
word-break: unset;
word-spacing: unset;
word-wrap: unset;
writing-mode: unset;
z-index: unset;

For future readers. I think this is what was meant but currently isn't really wide supported (see below):

CSS:

#someselector {
  all: initial;
}

#someselector * {
  all: unset
}

SCSS:

#someselector {
  all: initial;
  * {
    all: unset;
  }
}

• Supported in (source): Chrome 37, Edge 79, Firefox 27, IE 11, Opera 24, Safari 9.1, WebView Android 37, Chrome Android 37, Firefox for Android 27, Opera Android 24, Safari on iOS 9.3, Samsung Internet 3.0

• Not supported: Internet Explorer

There's a brand new solution found to this problem.

Use all: revert or all: unset.

From MDN:

> The revert keyword works exactly the same as unset in many cases. The > only difference is for properties that have values set by the browser > or by custom stylesheets created by users (set on the browser side).

> You need "A css rule available that would remove any styles previously set in the stylesheet for a particular element."

So, if the element have a class name like remove-all-styles:

Eg:

HTML:

<div class="remove-all-styles other-classe another-class"> 
   <!-- content -->
   <p class="text-red other-some-styles"> My text </p>
</div>

With CSS:

  .remove-all-styles {
    all: revert;
  }

Will reset all styles applied by other-class, another-class and all other inherited and applied styles to that div.

Or in your case:

/* mobile first */
.element {
   margin: 0 10;
   transform: translate3d(0, 0, 0);
   z-index: 50;
   display: block;
   etc..
   etc..
}

@media only screen and (min-width: 980px) {
  .element {
    all: revert;
  }
}

Will do.

> Here we used one cool CSS property with another cool CSS value.

> 1. revert > > Actually revert, as the name says, reverts that property to its > user or user-agent style. > > 2. all > > And when we use revert with the all property, all CSS properties > applied to that element will be reverted to user/user-agent styles.

Click here to know difference between author, user, user-agent styles.

For ex: if we want to isolate embedded widgets/components from the styles of the page that contains them, we could write:

.isolated-component {
 all: revert;
}

Which will reverts all author styles (ie developer CSS) to user styles (styles which a user of our website set - less likely scenario) or to user-agent styles itself if no user styles set.

More details here: https://developer.mozilla.org/en-US/docs/Web/CSS/revert

And only issue is the support: only Safari 9.1 and iOS Safari 9.3 have support for revert value at the time of writing.

So I'll say use this style and fallback to any other answers.

Let me answer this question thoroughly, because it's been a source of pain for me for several years and very few people really understand the problem and why it's important for it to be solved. If I were at all responsible for the CSS spec I'd be embarrassed, frankly, for having not addressed this in the last decade.

The Problem

You need to insert markup into an HTML document, and it needs to look a specific way. Furthermore, you do not own this document, so you cannot change existing style rules. You have no idea what the style sheets could be, or what they may change to.

Use cases for this are when you are providing a displayable component for unknown 3rd party websites to use. Examples of this would be:

1. An ad tag
2. Building a browser extension that inserts content
3. Any type of widget

Simplest Fix

Put everything in an iframe. This has it's own set of limitations:

1. Cross Domain limitations: Your content will not have access to the original document at all. You cannot overlay content, modify the DOM, etc.
2. Display Limitations: Your content is locked inside of a rectangle.

If your content can fit into a box, you can get around problem #1 by having your content write an iframe and explicitly set the content, thus skirting around the issue, since the iframe and document will share the same domain.

CSS Solution

I've search far and wide for the solution to this, but there are unfortunately none. The best you can do is explicitly override all possible properties that can be overridden, and override them to what you think their default value should be.

Even when you override, there is no way to ensure a more targeted CSS rule won't override yours. The best you can do here is to have your override rules target as specifically as possible and hope the parent document doesn't accidentally best it: use an obscure or random ID on your content's parent element, and use !important on all property value definitions.

The quick answer is use "all:revert"

.element {
  all:revert;
}

all:revert will RESET all the style properties on your element back to the original browser default UA style sheet property values. But it will not ERASE style properties like initial, returning them to a completely unstyled state.

In the case of text or inherited properties, "revert" resets your element's CSS property back to its inherited values coming from your "body" element or the browser's default UA style value, not to the property’s base style. For a non-inherited property, it resets it back again to the browser's UA default style sheet and not to the property’s base style. "all" allows all properties to be affected. This is likely what you want to see.

Problems Using "all:revert"

"all:revert" is a newer CSS declaration that only works in more modern HTML5 browsers (post-2015), and even then has very poor support in certain modern browsers like Internet Explorer 1-11, Edge Trident, and some mobile browsers. None of the older, non-HTML5 browsers (pre-2010) will understand this declaration, so it will be ignored by a wide range of browsers, old and new. (See my mixed CSS solution down below that has fixes for Internet Explorer).

Problems Using "initial"

You can use "initial" or "unset" but you have to manually apply them for each property, and what is even worse, they will not return properties to the element's default display values as set by each browser's default UA style sheet, but "initial" will essentially erase the element's property values and create a completely unstyled element. For example, "display:block" on block level elements will be erased. Because the style property still needs a default value of some kind all block and non-block level elements with "display" will be changed to "display:inline" when you use "display:initial". You do not want to ever do this as it erases your styles AND the browser's default UA element styles from the selected element completely.

My recommendation is AVOID using all:initial or any form of initial in CSS unless you are trying to erase an individual CSS property you cannot erase in any other way. Why? initial erases not just the styles you applied but all styles the browsers default UA style sheet applied. all:revert will not do this. In terms of using initial, it does have better support in Internet Explorer, as does its cousin, inherit. But only IE8+ understands initial. So, there are a wide range of problems with this property value. It is not reliable.

The reason CSS works this way is all HTML elements come without any styling until the browser applies a default user-agent style sheet that gives all the HTML elements a base style. All HTML elements really have NO STYLES, and other than "replaced" elements like textarea and buttons, look alike until each browser's default UA sheet is applied. "initial" and "unset" would wipe away most of that from the browser. "revert" at least preserves their basic style set applied by the user's browser, and is therefore superior to "initial" and "unset". You can review all the various default style sheets that come with browsers in the link below.

A LIST OF DEFAULT BROWSER STYLE SHEETS: https://meiert.com/en/blog/user-agent-style-sheets/

NOW FOR AN EVEN BETTER SOLUTION

There are two ideas here being confused:

1. The first idea is about "returning" styles back to a browser's UA style sheet value set (the style sheet that comes with the browser on install that defines what each element looks like). Each browser defines its own styles as to how elements should look by default. This idea is about returning all page styles back to each browsers native element styles.
2. The second idea is about "resetting" all default browser styles to a common look and feel shared by all browsers. People build special "reset" sheets to try and align all the browser elements to a common agreed on style, universally. This has nothing to do with a browsers default UA styles and more about "cleaning up" and aligning all browsers to a common base style. This is an additive process only.

Those are two very different concepts people here are confusing.

Because each browser often had default, out-of-the-box element and layout styles that looked slightly different, people came up with the idea of the "reset" or "reboot" style sheet to align all the browsers BEFORE applying custom CSS. Bootstrap now does this, for example. But that had nothing to do with people wanting to return to the browser's default look and feel.

The problem was not the building of these custom "reset" style sheets, it is figuring out what the default CSS was for each browser and each element BEFORE any styles were applied. Most found out you cant rebuild an existing clean cascade until you "clear out" all styles already applied. But how to get back to the default browser styling?

For some this meant going beyond returning the elements to the browsers UA style sheet that comes with the browser. Many wanted to reset back to "initial" property values which has NOTHING to do with the browser's default style, but really the properties defaults. This is dangerous as in the case of "display" pushes block level elements back to "inline" and breaks table layouts and other things.

So I do NOT agree with users here using "initial" to reset anything or custom reset classes that change every property back to some arbitrary base value set.

A better solution to me has always been to attempt to try and return all core element styling back to the browser's UA style sheet values, which is what all our end-users are using anyway. If you are creating a new website, you don't have to do this. You start with the browser's default styles and style over them. Its only after you've added third-party CSS products, or found yourself with complicated CSS cascades, that you want to figure out how to return to the browser default style sheet values.

For this reason, I'm for creating your own "reset" sheet to reset all the elements to one common style first that's shared by all old and new browsers as a first step. You then have a solid framework that's much easier to revert to without going back to the browser defaults. You are simply building on a reset common core set of element style values. Once build your own "reset" sheet, one that ADDS not ALTERS the browsers UA styles, you have a site that's very easy to modify.

The only problem remaining then is when you have a site that does NOT have such a reset sheet, or have that complex third party CSS and need to try and return to the browser UA styles. How do you do that?

I realize Internet Explorer has forced us too manually reset every property to get back to any sort of reset. But pushing those property values all back to "initial" destroys the browser UA style sheet values completely! BAD IDEA! A better way is to simply use "all:revert" for non-IE browsers on every element using a wildcard, and "inherit" only for a handful of inherited root-level properties found in the "html" and "body" elements that affect all inheriting children in the page. (see below). I'm NOT for these huge resets of properties using "initial" or going back to some imaginary standard we assume all browsers or IE will use. For starters "initial" has poor support in IE and doesn't reset values to element defaults, only property defaults. But its also pointless if you are going to create a reset sheet to align all elements to a common style. In that case its pointless to clear out styles and start over.

So here is my simple solution that in most cases does enough to reset what text-based values sift down into IE from the root and use "all:revert" for all non-IE browsers to force non-inherited values back to the browser's UA style sheet completely, giving you a true restart. This does not interfere with higher level classes and styles layered over your element styles, which should always be the goal anyway. Its why I'm NOT for these custom reset classes which is tedious and unnecessary and doesn't return the element to its browser UA style anyway. Notice the slightly more selective selectors below which would write over, for example, Bootstrap's "reboot" style values, returning them to the browser default styles. These would not reset element styles on elements for IE, of course, but for non-IE browsers and most inheritable text styling it would return elements in most agents to the UA style sheets that come with browsers:

:root, html {
    display: block;
    font-family: inherit;
    font-size: inherit;
    font-weight: inherit;
    line-height: inherit;
    -webkit-text-size-adjust: inherit;
    -webkit-tap-highlight-color: inherit;
    all: revert;
}

html body {
    display: block;
    font-family: inherit;
    font-size: inherit;
    font-weight: inherit;
    line-height: inherit;
    margin: inherit;
    padding: inherit;
    color: inherit;
    text-align: inherit;
    background-color: inherit;
    background: inherit;
    all: revert;
}

/* This rule attempts to manually reset all elements back to the 
UA browser style sheet using "revert" and the "wildcard" (*)
which resets all properties on all HTML elements.
This would overwrite most of Bootstraps "reboot" styles
on elements, for example.
Note: This selector should be ignored by IE. */

html body * {
    all: revert;
}

another ways:

1. include the css code(file) of Yahoo CSS reset and then put everything inside this DIV:

2. or use

• https://cssreset.com/scripts/vanilla-css-un-reset/
• https://cssreset.com/scripts/html5-doctor-css-reset-stylesheet/
• https://cssreset.com/scripts/eric-meyer-reset-css/
• https://cssreset.com/scripts/tripoli-css-reset-david-hellsing/
• https://cssreset.com/scripts/normalize-css/

If you happen to be using sass in a build system, one way to do this that will work in all the major browsers is to wrap all your style imports with a :not() selector like so...

:not(.disable-all-styles) {
  @import 'my-sass-file';
  @import 'my-other-sass-file';
}

Then you can use the disable class on a container and the sub-content won't have any of your styles.

<div class="disable-all-styles">
  <p>Nothing in this div is affected by my sass styles.</p>
</div>

Of course all your styles will now be prepended with the :not() selector, so it's a little fugly, but works well.

I do not recommend using the answer that has been marked as correct here. It is a huge blob of CSS which tries to cover everything.

I would suggest that you evaluate how to remove the style from an element on a per case basis.

Lets say for SEO purposes you need to include an H1 on a page which has no actual heading in the design. You might want to make the nav link of that page an H1 but ofcourse you do not want that navigation link to display as a giant H1 on the page.

What you should do is wrap that element in an h1 tag and inspect it. See what CSS styles are being applied specifically to the h1 element.

Lets say I see the following styles applied to the element.

//bootstrap.min.css:1
h1 {
    font-size: 65px;
    font-family: 'rubikbold'!important;
    font-weight: normal;
    font-style: normal;
    text-transform: uppercase;
}

//bootstrap.min.css:1
h1, .h1 {
    font-size: 36px;
}

//bootstrap.min.css:1
h1, .h1, h2, .h2, h3, .h3 {
    margin-top: 20px;
    margin-bottom: 10px;
}

//bootstrap.min.css:1
h1, h2, h3, h4, h5, h6, .h1, .h2, .h3, .h4, .h5, .h6 {
    font-family: inherit;
    font-weight: 500;
    line-height: 1.1;
    color: inherit;
}

//bootstrap.min.css:1
h1 {
    margin: .67em 0;
    font-size: 2em;
}

//user agent stylesheet
h1 {
    display: block;
    font-size: 2em;
    -webkit-margin-before: 0.67em;
    -webkit-margin-after: 0.67em;
    -webkit-margin-start: 0px;
    -webkit-margin-end: 0px;
    font-weight: bold;
}

Now you need to pin point the exact style which are applied to the H1 and unset them in a css class. This would look something like the following:

.no-style-h1 {
    font-size: unset !important;
    font-family: unset !important;
    font-weight: unset !important;
    font-style: unset !important;
    text-transform: unset !important;
    margin-top: unset !important;
    margin-bottom: unset !important;
    line-height: unset !important;
    color: unset !important;
    margin: unset !important;
    display: unset !important;
    -webkit-margin-before: unset !important;
    -webkit-margin-after: unset !important;
    -webkit-margin-start: unset !important;
    -webkit-margin-end: unset !important;
}

This is much cleaner and does not just dump a random blob of code into your css which you don't know what it's actually doing.

Now you can add this class to your h1

<h1 class="no-style-h1">
     Title
</h1>

BETTER SOLUTION

Download "copy/paste" stylesheet‎ to reset css properties to default (UA style):
https://github.com/monmomo04/resetCss.git

Thanks@Milche Patern!
I was really looking for reset/default style properties value. My first try was to copy the computed value from the browser Dev tool of the root(html) element. But as it computed, it would have looked/worked different on every system.
For those who encounter a browser crash when trying to use the asterisk * to reset the style of the children elements, and as I knew it didn't work for you, I have replaced the asterisk "*" with all the HTML tags name instead. The browser didn't crash; I am on Chrome Version 46.0.2490.71 m.
At last, it's good to mention that those properties will reset the style to the default style of topest root element but not to the initial value for each HTML element. ‎So to correct this, I have taken the "user-agent" styles of webkit based browser and implemented it under the "reset-this" class.

Useful link:

Download "copy/paste" stylesheet‎ to reset css properties to default (UA style):
https://github.com/monmomo04/resetCss.git

User-agent style:
https://stackoverflow.com/questions/6867254/browsers-default-css-for-html-elements/6867287#6867287<br> http://trac.webkit.org/browser/trunk/Source/WebCore/css/html.css

Css specifity (pay attention to specifity) :
https://css-tricks.com/specifics-on-css-specificity/

https://github.com/monmomo04/resetCss.git

You mentioned mobile-first sites... For a responsive design, it's certainly possible to override small-screen styles with large-screen styles. But you might not need to.

Try this:

.thisClass {
    /* Rules for all window sizes. */
}

@media all and (max-width: 480px) {
    .thisClass {
        /* Rules for only small browser windows. */
    }
}

@media all and (min-width: 481px) and (max-width: 960px) {
    .thisClass {
        /* Rules for only medium browser windows. */
    }
}

@media all and (min-width: 961px) {
    .thisClass {
        /* Rules for only large browser windows. */
    }
}

Those media queries don't overlap, so their rules don't override each other. This makes it easier to maintain each set of styles separately.

In my specific scenario i wanted to skip applying common styles to a specific part of the page, better illustrated like this:

<body class='common-styles'>
    <div id='header'>Wants common styles</div>
    <div id='container'>Does NOT want common styles</div>
    <div id='footer'>Wants common styles</div>
</body>

After messing with CSS reset which didn't bring much success (mainly because of rules precedence and complex stylesheet hierarchy), brought up ubiquitous jQuery to the rescue, which did the job very quickly and reasonably dirty:

$(function() {
    $('body').removeClass('common-styles');
    $('#header,#footer').addClass('common-styles');
});

(Now tell how evil it is to use JS to deal with CSS :-) )

For those of you trying to figure out how to actually remove the styling from the element only, without removing the css from the files, this solution works with jquery:

$('.selector').removeAttr('style');

if you set your CSS within classes, you can easly remove them using jQuery removeClass() Method. The code below removes .element class:

    <div class="element">source</div>   
    <div class="destination">destination</div>
      <script>
        $(".element").removeClass();
      </script>
    

If no parameter is specified, this method will remove ALL class names from the selected elements.

If anyone is coming here looking for an answer that utilizes iframe here it is

<iframe srcdoc="<html><body>your-html-here</body></html>" />

https://caniuse.com/iframe-srcdoc

Any chance you're looking for the !important rule? It doesn't undo all declarations but it provides a way to override them.

"When an !important rule is used on a style declaration, this declaration overrides any other declaration made in the CSS, wherever it is in the declaration list. Although, !important has nothing to do with specificity."

https://developer.mozilla.org/en-US/docs/CSS/Specificity#The_!important_exception